All tools
Browse all 590 free academic tools — calculators, converters, and references across 24 subjects.
Final Grade Calculator
What you need on your final exam.
GPA Calculator
Standard 4.0 scale, weighted or unweighted.
Weighted GPA
AP / IB / Honors with bonus points.
Cumulative GPA
Combine multiple semesters into one.
Semester GPA
Single semester with credit hours.
Grade Needed
Reverse-calculate from your target.
Test Grade
Correct over total → percentage + letter.
Class Grade
All assignments, weighted average.
GPA Goal Planner
The GPA you need in remaining credits to hit a target cumulative GPA.
Grade Curve Calculator
Curve a raw score with flat, linear-scale, or square-root methods.
Rubric Grade Calculator
Score a project from rubric criteria — overall % and letter grade.
GPA Retake Calculator
Recalculate your GPA after retaking a course — replacement or averaging.
Grade Distribution
Class average, spread, pass rate, and letter-grade breakdown from a score list.
Grading Scale Maker
Build a points-to-letter conversion table for any test total.
Word Counter
Words, characters, reading time — live as you type.
Citation Generator
APA, MLA, Chicago, Harvard, and IEEE citations in seconds.
Character Counter
With/without spaces. Tweet & SMS limits.
Reading Time
Estimate reading time at 250 WPM.
Words to Pages
By font, size, and line spacing.
Readability Score
Flesch-Kincaid, Gunning Fog, SMOG.
Words to Minutes
Speaking time from a word count.
Thesis Statement Builder
Topic + claim + reasons → a thesis.
Syllable Counter
Count syllables in words and text.
Lorem Ipsum Generator
Placeholder text by paragraphs, sentences, or words.
Word Frequency Counter
Count how often each word appears in your text.
Passive Voice Finder
Highlight likely passive-voice sentences in your writing.
Text Diff Checker
Compare two blocks of text and see what was added or removed.
Sentence Length Analyzer
Average sentence length and the longest sentences in your text.
Random Word Generator
Generate random words for brainstorming and writing prompts.
Line Sorter & Deduper
Sort lines alphabetically or by length and remove duplicates.
Text Cleaner
Trim whitespace, remove blank lines, and tidy up messy text.
Essay Outline Builder
Turn a thesis and key points into a structured essay outline.
BibTeX Converter
Turn BibTeX entries into a formatted reference list in four styles.
Annotated Bibliography
Build an entry from its three parts, with structural checks.
Pomodoro Timer
Focus timer with a visual ring and breaks.
Exam Countdown
Days, hours, minutes to your exam.
Flashcards
Create, save, and study locally.
Cornell Notes
Editable template, exportable.
Reading Speed Test
Measure your reading WPM.
Typing Speed Test
WPM and accuracy, live feedback.
Study Planner
Split weekly hours across subjects.
Mind Map Maker
Outline → branching mind map.
Spaced Repetition Scheduler
Next review interval for a flashcard using the SM-2 algorithm.
Forgetting Curve Calculator
Estimated memory retention over time from the forgetting curve.
Study Hours Planner
Weekly and semester study hours from your credit load.
Focus & Break Planner
Fit focus and break cycles into your time with proven work rhythms.
Attendance Calculator
How many classes you can miss and stay above the required attendance %.
Class Schedule Maker
Build a printable weekly class timetable, saved in your browser.
Reading Schedule Planner
Split a reading assignment into pages per day before it’s due.
Scientific Calculator
Full function with history.
Percentage Calculator
Percent of, increase, decrease, change.
Quadratic Solver
ax² + bx + c = 0, step by step.
Matrix Calculator
Add, subtract, multiply, determinant.
Trigonometry
sin, cos, tan + inverse functions.
Fraction Calculator
+ − × ÷ with simplification.
Derivative Calculator
Step by step, with the rules used.
Integral Calculator
Definite & indefinite, with steps.
System of Equations
2×2 and 3×3 linear systems.
Polynomial Roots
All real and complex roots.
Limit Calculator
Estimate a limit from both sides.
Logarithm Calculator
log, ln, log₂, and any base.
Factorial Calculator
n! exactly, with expansion.
Combinations & Permutations
nCr and nPr, exact.
Fraction ↔ Decimal ↔ %
Convert between all three forms.
Slope Calculator
Slope, intercept, and line equation from two points.
GCD & LCM
Greatest common divisor, least common multiple, and prime factors.
Significant Figures
Count significant figures and round to a given number.
Ratio Calculator
Simplify ratios and solve proportions.
Sequences
Arithmetic and geometric nth term and sum.
Vector Calculator
Add, subtract, dot/cross product, magnitude.
Complex Numbers
Add, multiply, modulus, and conjugate.
Exponent Calculator
Powers and the laws of exponents.
Simplify Radicals
Reduce a square root to simplest radical form.
Modulo Calculator
Remainder of a division (a mod n).
Percent Error
Compare a measured value to the true value.
Prime Number Checker
Test if a number is prime and factor it.
Rounding Calculator
Round to decimals, places, or significant figures.
Long Division Calculator
Divide two numbers with the full long-division working shown.
Synthetic Division Calculator
Divide a polynomial by (x − c) with the synthetic-division steps.
Completing the Square
Rewrite a quadratic as a(x − h)² + k, step by step.
Partial Fractions Calculator
Decompose a rational function into partial fractions with steps.
Polynomial Long Division
Divide one polynomial by another with the long-division working.
Prime Factorization Calculator
Break a number into its prime factors with the division steps.
Mixed Numbers
Mixed number ↔ improper fraction, both ways with steps.
Order of Operations
PEMDAS / BODMAS, evaluated step by step.
Factoring Calculator
Factor a polynomial and see which method did the work.
Inequality Calculator
Solve linear, quadratic and polynomial inequalities with a sign chart.
Absolute Value Solver
Solve |ax + b| equations and inequalities, case by case.
Domain & Range
Find where a function is defined, and its range where exact.
Inverse Function
Find f⁻¹(x) for linear, rational, root and log functions.
Eigenvalues
Eigenvalues and the characteristic polynomial of a matrix.
Binomial Expansion
Expand (a + b)ⁿ with exact coefficients, term by term.
Riemann Sum
Approximate an integral with rectangles, and watch it converge.
Numerical Integration
Simpson, trapezoid and midpoint compared, with error orders.
Taylor Series
Build a Taylor polynomial to any order, with its error.
Modular Arithmetic
Modular inverses, huge powers, congruences and the CRT.
Newton–Raphson Solver
Solve f(x) = 0 by Newton, secant, bisection or false position.
Interpolation Calculator
Read between data points, with the divided-difference table.
Conic Sections
Identify any conic from its general equation, rotated ones included.
Polar Coordinates
Convert either way with the correct quadrant and exact π forms.
Parametric Equations
Plot x(t) and y(t), with tangent slope, arc length and turning points.
Arc Length & Sector
Arc length, sector area and chord from a radius and an angle.
Radians & Degrees
Convert either way, with the exact multiple of π alongside.
Function Composition
Build f(g(x)) and g(f(x)) by substitution, and evaluate both.
Periodic Table
Interactive, filterable, element details.
Molar Mass
Enter a formula → molecular weight.
pH Calculator
From H⁺ concentration or Ka.
Equation Balancer
Auto-balance chemical equations.
Stoichiometry Calculator
Mole ratios and masses from a reaction.
Dilution Calculator
Solve C₁V₁ = C₂V₂ for any variable.
Ideal Gas Law
PV = nRT, solve for any variable.
Concentration Calculator
Molarity, molality, and normality.
Empirical Formula
Simplest whole-number atom ratio.
Buffer pH Calculator
Henderson–Hasselbalch buffer pH.
Percent Yield
Actual ÷ theoretical yield × 100.
Limiting Reagent
Find the limiting reactant from moles and coefficients.
Half-Life Calculator
Radioactive decay: remaining amount over time.
Gas Laws
Boyle, Charles, and the combined gas law.
Titration Calculator
Find unknown concentration from titration data.
Percent Composition
Mass percent of each element in a formula.
Boiling & Freezing Point
Colligative shifts: ΔT = i·K·m.
Electron Configuration
Electron configuration of any element.
Equilibrium Constant (K)
Compute K from equilibrium concentrations.
Mole Calculator
Convert between grams, moles, and particles.
Henderson-Hasselbalch Calculator
Buffer pH from pKa and the acid/base ratio.
Ka to pKa Converter
Convert between the acid constant Ka and pKa.
Beer-Lambert Law Calculator
Absorbance from molar absorptivity, path length, and concentration.
Reaction Rate Calculator
Reaction rate from the rate constant and reactant concentrations.
Arrhenius Equation Calculator
Rate constant or activation energy from the Arrhenius equation.
Nernst Equation Calculator
Cell potential from standard potential and the reaction quotient.
Gibbs Free Energy
ΔG from ΔH, ΔS and temperature, with the crossover point.
Hess’s Law
Add, scale and reverse step enthalpies to find ΔH.
Solubility Product
Molar solubility from Ksp, the common ion effect, and precipitation.
Electrolysis
Mass deposited from current and time, or the current a mass needs.
Oxidation Numbers
Assign an oxidation state to every element, with the rule used.
Quantum Numbers
Check whether a set of quantum numbers is allowed, and name it.
Bond Energy
Estimate a reaction’s enthalpy from bonds broken and formed.
Kinematics Solver
SUVAT equations of motion.
Projectile Motion
Range, height, and flight time.
Force Calculator
F = ma, solve for any variable.
Density Calculator
ρ = m / V, solve for any variable.
Wave Speed Calculator
v = fλ, speed, frequency, wavelength.
Pendulum Period
T = 2π√(L/g), period or length.
Specific Heat
Q = mcΔT, solve for any variable.
Lens Equation
1/f = 1/dₒ + 1/dᵢ, with magnification.
Kinetic Energy
KE = ½mv², solved for any variable.
Potential Energy
Gravitational PE = mgh.
Work & Power
Work = force × distance; power = work ÷ time.
Momentum & Impulse
p = mv and impulse = force × time.
Free Fall
Drop time and impact speed under gravity.
Torque Calculator
Torque τ = r × F × sin θ.
Centripetal Force
F = mv² ÷ r for circular motion.
Gravitational Force
Newton's law of gravitation, F = G·m₁m₂ ÷ r².
Hooke's Law
Spring force F = k × x.
Efficiency
Useful output ÷ total input × 100.
Snell's Law
Refraction: n₁ sin θ₁ = n₂ sin θ₂.
Pressure Calculator
Pressure from force and area, P = F ÷ A.
Acceleration Calculator
Acceleration from a change in velocity over time.
Friction Calculator
Friction force from the coefficient and normal force.
Doppler Effect Calculator
Observed frequency shift for a moving source or observer.
Escape Velocity Calculator
Speed needed to escape a planet or star from its mass and radius.
Orbital Period Calculator
Orbital period from the semi-major axis and central mass.
Bernoulli Equation Calculator
Pressure or speed along a streamline from Bernoulli’s equation.
Stefan-Boltzmann Calculator
Radiated power from temperature, area, and emissivity.
Projectile Range Calculator
Range, max height, and flight time from launch speed and angle.
Terminal Velocity Calculator
Terminal velocity from mass, area, drag coefficient, and air density.
Error Propagation
Combine measurement uncertainties through a calculation.
Coulomb’s Law
Force between two point charges, attracting or repelling.
Collision Calculator
Final velocities in one dimension, with the energy audit.
Buoyancy Calculator
Buoyant force, apparent weight, and float or sink.
Latent Heat
Heat to melt, freeze, boil or condense a given mass.
Photon Energy
Wavelength, frequency and energy, plus de Broglie.
Rotational Kinematics
Angular velocity, acceleration, displacement and time.
Banked Curve
Ideal banking angle, and the safe speed band once friction is included.
Punnett Square
Mono- and dihybrid crosses, visualized.
Hardy-Weinberg
Allele & genotype frequencies.
Allele Frequency
p and q from genotype counts.
DNA Codon Translator
Translate DNA/RNA into amino acids.
Serial Dilution
Concentration at every tube.
Dihybrid Cross
Two-trait Punnett square and 9:3:3:1 ratio.
Surface-Area-to-Volume
SA:V ratio for cells and shapes.
Population Growth
Exponential and logistic growth models.
Microscope Magnification
Total magnification from objective and eyepiece.
Michaelis-Menten Calculator
Reaction rate from Vmax, Km, and substrate concentration.
Cell Doubling Time Calculator
Doubling time and growth rate from a population over time.
Osmolarity Calculator
Osmolarity from molar concentration and particles per formula unit.
DNA Molecular Weight Calculator
Molecular weight of DNA or RNA from its length.
GC Content Calculator
Percentage of G and C bases in a DNA sequence.
DNA Concentration Calculator
Nucleic acid concentration and purity from A260/A280 readings.
Reverse Complement
The opposite strand, written 5′ → 3′.
Primer Melting Temperature
Tm by nearest-neighbour thermodynamics, with salt and concentration.
Protein Molecular Weight
MW, composition and extinction coefficient from a sequence.
Mitosis & Meiosis
Chromosome, chromatid and DNA counts at every stage, for any 2n.
Standard Deviation
Mean, variance, and SD for any dataset.
P-Value Calculator
From a test statistic and distribution.
Confidence Interval
For a mean or proportion.
Z-Score Calculator
Standardize a value and find its percentile.
Normal Distribution
Probabilities under the bell curve.
T-Test Calculator
One- and two-sample tests with p-value.
Chi-Square Calculator
Goodness-of-fit from observed vs expected.
Correlation Calculator
Pearson's r, r², and significance.
Sample Size Calculator
Participants needed for a margin of error.
ANOVA Calculator
One-way analysis of variance, F-table.
Mean, Median, Mode
Mean, median, mode, range, and quartiles from a data set.
Linear Regression
Least-squares line, slope, intercept, and r².
Percentile Calculator
Percentile rank of a value, and value at a percentile.
Binomial & Poisson
Binomial and Poisson probabilities.
Probability Calculator
Single and combined event probabilities.
Effect Size Calculator
Cohen’s d effect size from two group means and standard deviations.
Margin of Error Calculator
Margin of error for a survey proportion at a confidence level.
Five-Number Summary
Min, Q1, median, Q3, max, IQR, and outliers with a box plot.
Weighted Mean Calculator
Weighted average from value and weight pairs.
Geometric Mean Calculator
Geometric mean of a set of positive numbers.
Coefficient of Variation
Relative variability — standard deviation as a percent of the mean.
Test Item Analysis
Difficulty, discrimination, point-biserial, and KR-20 from a response matrix.
Cronbach’s Alpha
Scale reliability from item variances or the average inter-item correlation.
Split-Half Reliability
Correct a half-test correlation up to full length with Spearman-Brown.
Cohen’s Kappa
Chance-corrected agreement between two raters on a 2×2 table.
Fleiss’ Kappa
Agreement across three or more raters and any number of categories.
Intraclass Correlation
Single-rater and average-rater ICC from an ANOVA mean-square table.
Mann-Whitney U Test
Nonparametric comparison of two independent groups, with U, z, and p.
Wilcoxon Signed-Rank
Nonparametric test for paired data, with W, z, p, and effect size.
Kruskal-Wallis Test
Nonparametric ANOVA across three or more groups, with H and p.
McNemar’s Test
Test a change in paired yes/no data, with the exact binomial alternative.
Odds Ratio & Risk Ratio
Odds ratio and risk ratio from a 2×2 table, with confidence intervals.
Sensitivity & Specificity
Diagnostic accuracy from TP, FP, FN, and TN, with likelihood ratios.
APA Results Formatter
Format a t, F, χ², or r result in APA 7 style, ready to paste.
Bayes’ Theorem
Update a probability with evidence, with the frequency table.
Expected Value
E(X) for a discrete distribution, with variance and SD.
Standard Error
SE of a mean or proportion, with margin and interval.
Power Analysis
Participants needed for a target power, or the power you already have.
Bootstrap Intervals
Resampling intervals for the median and other formula-free statistics.
Logistic Regression
Fit a binary outcome, with odds ratios and their confidence intervals.
Tukey HSD
Every pairwise comparison after an ANOVA, with adjusted p-values.
Levene’s Test
Test whether groups have equal spread, before an ANOVA or t-test.
Shapiro–Wilk Test
Test a sample for normality, with the Q–Q plot alongside.
Critical Value Calculator
Critical values for z, t, χ² and F from α and degrees of freedom.
GPA Scale Converter
Convert a GPA between US, UK, German, Indian, and percentage scales.
IELTS ↔ TOEFL
Convert between IELTS band and TOEFL iBT score.
SAT ↔ ACT
Convert between SAT total and ACT composite scores.
Duolingo → IELTS
Convert a Duolingo English Test score to an IELTS band.
GRE Percentile
GRE Verbal/Quant scaled score to percentile.
GMAT Percentile
GMAT total score (200–800) to percentile.
Old SAT → New SAT
Convert between the 2400 and 1600 SAT scales.
CEFR ↔ IELTS / TOEFL
Map a CEFR level (A1–C2) to IELTS bands and TOEFL scores.
PTE ↔ IELTS
Convert PTE Academic scores to IELTS bands (and approx. TOEFL).
IB → GPA
Estimate a US 4.0 GPA from IB diploma grades.
A-Level → GPA
Estimate a US 4.0 GPA from A-Level grades.
ECTS Credit Converter
Convert ECTS credits to US credit hours and study hours.
UK Class ↔ GPA
Map a UK degree classification to an approximate US GPA.
Percentage to Letter Grade
Convert a percentage to a US letter grade and GPA.
IELTS Band Score Calculator
Overall IELTS band from your four section scores, with correct rounding.
ACT Composite Score Calculator
ACT composite score from your English, Math, Reading, and Science scores.
SAT Superscore Calculator
Your best SAT superscore from the top section scores across sittings.
German Grade Converter
Convert a foreign grade to the German 1–5 scale with the Bavarian formula.
Indian CGPA to Percentage
Convert between CGPA and percentage using the CBSE and 10-point scales.
TOEFL Score Calculator
TOEFL iBT total from your four section scores, with a CEFR level.
Canadian GPA Converter
Convert a Canadian percentage to a 4.0 GPA and letter grade.
Australian GPA (7-Point)
Convert an Australian mark to the 7-point GPA scale and US 4.0.
French Grade to GPA
Convert a French grade out of 20 to a US 4.0 GPA and mention.
Chinese GPA Converter
Convert a Chinese percentage to a 4.0 GPA using the WES scale.
SAT Score to Percentile
The national percentile for an SAT total score (400–1600).
GCSE 9-1 Grade Converter
Convert between GCSE 9–1 numeric grades and old A*–G letters.
JLPT Score to CEFR
Check a JLPT total against the pass mark and the official CEFR correspondence.
TOPIK Score to Level
Turn a TOPIK I or II total score into the level it awards.
Cambridge Scale to CEFR
Convert a Cambridge English Scale score to its CEFR level.
TCF Score to CEFR
Convert a TCF French test score to its CEFR level.
HSK Levels & CEFR
HSK 2.0 and 3.0 levels, vocabulary targets, and the disputed CEFR alignment.
Language Exams by CEFR
Which certificate proves each CEFR level, across eight languages.
Italian Grade to GPA
Italian exam grades out of 30, including 30 e lode, on a US 4.0 GPA.
Dutch Grade to GPA
Dutch cijfers on the 1–10 scale converted to a US 4.0 GPA.
Mexican Grade to GPA
Mexican calificaciones to a US 4.0 GPA, with the 6, 7, or 8 pass mark.
Nigerian CGPA to GPA
Nigerian 5-point CGPA to a US 4.0 GPA and the NUC degree class.
Pakistani Grade to GPA
Pakistani university percentages to letter grades and a 4.0 GPA.
Bangladeshi Grade to GPA
Bangladeshi percentages to UGC letter grades and the 4.00 scale.
Vietnamese Grade to GPA
Vietnamese 10-point điểm to a US 4.0 GPA and letter grade.
Indonesian IPK to GPA
Indonesian IPK on the 4.00 scale, with the graduation predicate.
Polish Grade to GPA
Polish oceny from 2 to 5, half steps included, on a US 4.0 GPA.
Greek Grade to GPA
Greek βαθμοί — Άριστα to Καλώς — converted to a US 4.0 GPA.
Turkish Grade to GPA
Turkish 100-point marks to YÖK letters and the 4.00 scale.
Japanese Grade to GPA
Japanese 100-point marks to 秀/優/良/可 and a US 4.0 GPA.
Korean GPA to 4.0
Convert a Korean 4.5 or 4.3 GPA to the US 4.0 scale.
Brazilian Grade to GPA
Brazilian notas and the CR on the 0–10 scale to a US 4.0 GPA.
Spanish Grade to GPA
Spanish notas — Sobresaliente to Suspenso — on a US 4.0 GPA.
Russian Grade to GPA
Russian 5, 4, and 3 marks converted to a US 4.0 GPA.
LSAT Percentile
Every score from 120 to 180 with its percentile rank.
MCAT Percentile
Every total from 472 to 528 with its percentile rank.
ASVAB AFQT Score
What an AFQT score means, and the published branch minimums.
Unit Converter
Length, mass, temperature, volume, and more.
Random Number & Picker
Random numbers or pick a name from a list.
Study Abroad Budget
Total cost of a program in one currency.
Wheel of Names
Spin a wheel to pick a random winner.
Markdown Editor
Write notes in Markdown, live preview.
Case Converter
UPPER, lower, Title, Sentence, camel, snake, kebab.
Color Converter
Convert between HEX, RGB, and HSL.
Password Generator
Strong random passwords, in your browser.
Fuel Cost Calculator
Trip fuel cost from distance, fuel economy, and price.
Fuel Economy Converter
Convert between MPG, L/100km, and km/L fuel economy.
Coin Flip
Flip a fair coin — heads or tails — one or many at a time, with a running tally.
Dice Roller
Roll d4–d100 dice with a modifier and see each die plus the total.
Aspect Ratio Calculator
Simplify a resolution to its aspect ratio or resize keeping the ratio.
Pixel Density (PPI) Calculator
Calculate screen pixel density (PPI) from resolution and diagonal size.
Color Contrast Checker
Check the WCAG contrast ratio between two colors and its AA/AAA rating.
Timesheet Calculator
Add up weekly work hours from daily start/end times, breaks, and overtime.
Image Resizer
Resize and compress an image to JPEG, WebP, or PNG without uploading it.
Seating Chart Maker
Arrange a roster into rows, pairs, or a horseshoe, and print it.
Random Group Generator
Split a list of names into balanced random groups or teams.
Greek Alphabet
All 24 letters with names and uses.
Math Symbols
Logic, sets, operators, calculus.
Roman Numeral Converter
Numbers ↔ Roman numerals, 1–3999.
Number Base Converter
Binary, octal, decimal, hex.
Grading Systems Explained
Grades by country: US, UK, Germany…
Academic Calendar Comparison
When the school year starts, by country.
Scientific Notation Converter
a × 10ⁿ, engineering, and E-notation.
Metric Prefix Converter
Convert between SI prefixes (kilo, milli, …).
Physical Constants
Reference table of common physics constants.
Multiplication Table
Times tables grid up to any number.
Morse Code Translator
Translate text to and from Morse code.
NATO Phonetic Alphabet
Spell text with the NATO phonetic alphabet (Alfa, Bravo, …).
Number to Words Converter
Write numbers in words for cheques and formal writing.
Trig Identities
Pythagorean, double-angle, sum, and half-angle trig identities to copy.
Derivative Rules
Power, product, quotient, and chain rules plus common derivatives.
Integral Table
Common indefinite integrals and integration rules to copy.
Unit Circle
Angles in degrees and radians with sine, cosine, and tangent values.
Algebra Formulas
Quadratic formula, factoring, exponent, and logarithm rules to copy.
Geometry Formulas
Area, perimeter, surface area, and volume formulas for common shapes.
Cyrillic Alphabet
The 33 Russian Cyrillic letters with names, transliteration, and sounds.
Hiragana & Katakana Chart
The Japanese kana with romaji — all 46 hiragana and katakana, searchable.
Korean Alphabet (Hangul)
The Korean alphabet: 14 consonants and 10 vowels with romanization.
Arabic Alphabet
All 28 Arabic letters with sounds and positional forms.
Hebrew Alphabet
All 22 Hebrew letters with sounds and gematria values.
Braille Alphabet
Braille letters and digits, with a text converter.
Z-Score Table
Standard normal areas for every z from −3.49 to 3.49.
T Distribution Table
Critical t values by degrees of freedom, one- and two-tailed.
Chi-Square Table
Critical χ² values for every upper-tail area and df.
F Distribution Table
Critical F values at α = 0.10, 0.05, 0.025 and 0.01.
Physics Formulas
Kinematics, forces, energy, waves, circuits, and gravitation.
Statistics Formulas
Descriptive measures, probability, intervals, tests, and effect sizes.
Chemistry Formulas
Moles, gas laws, solutions, thermochemistry, equilibrium, and rates.
Polyatomic Ions
Every common polyatomic ion with its formula and charge.
Solubility Rules
Which ionic compounds dissolve, and the exceptions.
Molecular Geometry
Every VSEPR shape by steric number, with bond angles.
Amino Acid Chart
All twenty residues with masses, classes, pKa and codons.
Medical Terminology
Decode clinical terms from their prefixes, roots and suffixes.
ASL Alphabet
What each digit does for all 26 letters, digit by digit.
Transition Words
87 linking words by what they signal and how to punctuate them.
Laplace Transform Table
Transform pairs, shifting theorems and convolution.
Limit Rules
Limit laws, standard limits, indeterminate forms, and asymptotes.
Series & Convergence
Maclaurin expansions with intervals, plus every convergence test.
Spanish Verb Conjugator
Conjugate Spanish verbs, 5 tenses.
French Verb Conjugator
Conjugate French verbs, 4 tenses.
German Verb Conjugator
Präsens, Präteritum, and Futur I.
Italian Verb Conjugator
Conjugate Italian verbs, 4 tenses.
Latin Noun Declension
Decline Latin nouns, all six cases.
Latin Verb Conjugation
Present, imperfect, future — 5 conjugations.
French Numbers in Words
Write any number in French, with the 70/80/90 forms handled.
Spanish Numbers in Words
Write any number in Spanish, with gender and apocope handled.
German Numbers in Words
Write any number in German, as one compound word.
German Cases & Articles
Der/die/das and ein declension across all four German cases.
False Friends Reference
Words that look alike across languages but mean something else.
IPA Pronunciation Reference
IPA vowels and consonants with example words and descriptions.
Portuguese Verb Conjugator
Conjugate Portuguese regular and common irregular verbs across five tenses.
Italian Numbers in Words
Convert a number into Italian words, with elision (ventuno) and accents (ventitré).
Portuguese Numbers in Words
Convert a number into Portuguese words (cem vs cento, the “e” connector; EP & BR).
Dutch Numbers in Words
Convert a number into Dutch words, with unit-before-tens (eenentwintig) and trema.
Latin Numbers in Words
Convert a number into Latin cardinals, including the subtractive 18/19 forms.
Russian Numbers in Words
Convert a number into Russian words, with correct тысяча agreement.
Japanese Numbers
Write any number as a Japanese numeral (kanji + romaji).
Chinese Numbers
Write any whole number in Mandarin Chinese (hanzi + pinyin).
Korean Numbers
Any number in both Korean systems, Sino and Native.
Greek Transliterator
Romanise Greek with the ELOT 743 passport table or ISO 843 transliteration.
Cyrillic Transliterator
Transliterate Russian with the ICAO passport table or the BGN/PCGN standard.
Kana to Romaji
Convert hiragana and katakana to Hepburn romaji, with gemination and long vowels.
Hangul Romanizer
Romanise Korean with the official standard, including the sound-change rules.
Compound Interest
Growth with compounding, A = P(1 + r/n)^(nt).
Simple Interest
Interest = principal × rate × time.
Loan & EMI Calculator
Monthly payment, total interest, and schedule.
Discount Calculator
Sale price and amount saved from a percent off.
Tip Calculator
Tip amount and total, split across people.
Savings Goal
Monthly saving needed to reach a target.
ROI Calculator
Return on investment, gain, and annualized return.
Markup & Margin
Profit markup and margin from cost and price.
Break-Even Calculator
Units to sell to cover fixed and variable costs.
Inflation Calculator
How prices and buying power change over time.
Salary Converter
Hourly, weekly, monthly, and annual pay.
Sales Tax Calculator
Tax amount and total from a price and rate.
Mortgage Calculator
Monthly payment, total interest, and amortization from loan terms.
APR to APY Converter
Convert between APR and APY for any compounding frequency.
Credit Card Payoff Calculator
Months to clear a card balance and the total interest paid.
50/30/20 Budget Calculator
Split take-home pay into needs, wants, and savings.
Net Worth Calculator
Total assets minus liabilities to find your net worth.
Rule of 72 Calculator
Estimate how long an investment takes to double.
Cost Per Unit Calculator
Find the unit price and compare which option is cheaper.
Present Value Calculator
Discount a future amount back to what it is worth today.
Future Value Calculator
Grow a present sum to its value after compounding.
CAGR Calculator
Compound annual growth rate between a start and end value.
Annuity Payment Calculator
Payment for a present value or to reach a savings goal.
NPV Calculator
Net present value of a cash-flow series at a discount rate.
Depreciation Calculator
Straight-line depreciation and a year-by-year schedule.
Profit Margin Calculator
Gross, operating, and net profit margin from revenue and costs.
Bill Split Calculator
Split a bill evenly across people, with optional tip.
CAPM Calculator
Cost of equity from the risk-free rate, beta, and the market return.
WACC Calculator
Blended cost of capital from the equity and debt mix, with the tax shield.
IRR Calculator
The discount rate that makes NPV zero, with a hurdle-rate comparison.
Payback Period
How long until a project repays its investment, with and without discounting.
Bond Price & YTM
Price a bond from its yield, or solve for yield to maturity from the price.
Economic Order Quantity
Optimal order size, reorder point, and total inventory cost.
Financial Ratios
Current, quick, and cash ratios, debt-to-equity, and interest coverage.
DuPont ROE Analysis
Split ROE into margin, asset turnover, and financial leverage.
Inventory Turnover
How often stock is sold and replaced, and how long it sits.
Operating Leverage
DOL, DFL, and DCL — how sales changes amplify into profit changes.
EPS & P/E Ratio
Earnings per share, P/E, earnings yield, payout ratio, and market cap.
Truth Table Generator
Truth table for any boolean expression.
Two's Complement
Signed binary ↔ decimal conversion.
Boolean Algebra
Evaluate and simplify boolean expressions.
ASCII & Unicode Lookup
Characters ↔ ASCII / Unicode code points.
Bitwise Calculator
AND, OR, XOR, NOT, and bit shifts.
Data Storage Converter
Bytes, KB, MB, GB, TB — binary and decimal.
Base64 Encode & Decode
Convert text to and from Base64.
URL Encode & Decode
Percent-encode text for URLs, or decode it back.
JSON Formatter
Pretty-print, minify, and validate JSON in your browser.
SHA-256 Hash Generator
Generate a SHA-256 hash of any text.
HTML Entity Encode & Decode
Convert characters to HTML entities and back.
IP Subnet Calculator
Network, broadcast, mask, and host range from an IP and CIDR.
Regex Tester
Test a regular expression against text and see matches.
CSV to JSON Converter
Convert CSV to a JSON array and back, in your browser.
Text to Binary Converter
Convert text to 8-bit binary and decode binary back to text.
Caesar Cipher
Encode or decode a Caesar shift cipher, including ROT13.
Vigenère Cipher
Encode or decode a Vigenère cipher with a keyword.
Big-O Complexity Reference
Common time complexities with examples and a growth comparison.
Hamming Distance Calculator
Count the differing positions between two equal-length strings.
Hexadecimal Calculator
Add, subtract, multiply, and divide hexadecimal numbers.
IEEE 754 Float Converter
The sign, exponent, and mantissa bits of a 32-bit float.
Set Operations Calculator
Union, intersection, and difference of two sets.
Gray Code Converter
Convert between binary and reflected Gray code.
Download Time Calculator
Estimate how long a download takes from file size and connection speed.
UUID Generator
Generate random version-4 UUIDs (GUIDs), one or many, with copy.
JWT Decoder
Decode a JWT’s header and payload and read its claims — client-side, no verification.
Slug Generator
Turn a title into a clean URL slug — lowercase, hyphens, no accents.
Cron Expression Parser
Translate a cron schedule into plain English and see when it next runs.
Karnaugh Map
Minimise a Boolean function, with the map and every prime implicant.
Sorting Algorithms
Trace bubble, merge, quick and heap sort on your own numbers.
Time Zone Converter
Convert a time between any two time zones.
Date Calculator
Days between dates, or add/subtract days.
Age Calculator
Exact age in years, months, and days.
Stopwatch & Timer
Stopwatch with laps and a countdown timer.
Business Days Calculator
Count working days (weekdays) between two dates.
Unix Timestamp Converter
Convert between Unix epoch time and a human date.
Week Number Calculator
Find the ISO week number for any date.
Days Until Date
Count down the days until any future date.
Time Duration Calculator
Add, subtract, or find the duration between two times.
Hours Calculator
Hours worked from a start and end time, minus breaks.
Leap Year Checker
Check if a year is a leap year and why.
Day of the Week
The weekday for any date, plus day of year and ISO week.
Military Time Converter
Convert between 12-hour AM/PM and 24-hour military time.
BMI Calculator
Body mass index from height and weight.
BMR & Calorie Calculator
Basal metabolic rate and daily calories (TDEE).
Body Fat Calculator
Estimate body-fat percentage with the US Navy tape method.
TDEE Calculator
Total daily energy expenditure from BMR and activity level.
Macro Calculator
Split daily calories into protein, carbohydrate, and fat grams.
Water Intake Calculator
Estimate daily water needs from body weight and activity.
Ideal Weight Calculator
Healthy weight range from height with classic formulas.
Calorie Goal Calculator
Daily calories to lose, maintain, or gain weight at a target rate.
Heart Rate Zone Calculator
Training heart-rate zones from your age and resting rate.
Sleep Cycle Calculator
Best bedtimes or wake times based on 90-minute sleep cycles.
Running Pace Calculator
Pace, speed, distance, or finish time for runs and races.
Steps to Calories Calculator
Distance and calories burned from your step count.
Calories Burned Calculator
Calories burned from an activity’s MET value, weight, and time.
One-Rep Max Calculator
Estimate your 1RM from reps and weight with the Epley and Brzycki formulas.
Body Surface Area Calculator
Calculate BSA from height and weight with the Mosteller and Du Bois formulas.
Waist-to-Hip Ratio Calculator
Work out your waist-to-hip ratio and WHO health-risk category.
VO₂ Max Estimator
Estimate VO₂ max from a Cooper run test or your resting heart rate.
Lean Body Mass Calculator
Estimate lean body mass with the Boer and James formulas.
Protein Intake Calculator
Find your daily protein target in grams by body weight and goal.
Distance & Midpoint
Distance and midpoint between two points.
Pythagorean Theorem
Solve a² + b² = c² for any missing side.
Area & Volume
Area and volume of common 2D and 3D shapes.
Triangle Solver
Solve a triangle from sides and angles (SSS, SAS, ASA, AAS).
Circle Calculator
Radius, diameter, circumference, and area of a circle.
Sphere Calculator
Volume and surface area of a sphere from its radius.
Cylinder Calculator
Volume and surface area of a cylinder from radius and height.
Cone Calculator
Volume, slant height, and surface area of a cone.
Rectangular Prism Calculator
Volume, surface area, and diagonal of a box from its sides.
Regular Polygon Calculator
Area, perimeter, and interior angle of a regular polygon.
Recipe Scaler
Scale recipe ingredients up or down by a factor or new serving size.
Cooking Measurement Converter
Convert between teaspoons, tablespoons, cups, millilitres, and ounces.
Oven Temperature Converter
Convert oven temperatures between Fahrenheit, Celsius, and gas mark.
Cups to Grams Converter
Convert cups to grams for flour, sugar, butter, and more.
Butter Converter
Convert butter between sticks, tablespoons, cups, grams, and ounces.
Air Fryer Converter
Adjust oven time and temperature for an air fryer.
Baker’s Percentage Calculator
Ingredients as a percentage of flour, plus dough hydration.
Ingredient Substitutions
Searchable common cooking and baking substitutions with ratios.
Yeast Converter
Convert between instant, active dry, and fresh yeast by weight.
Coffee Ratio Calculator
Coffee-to-water ratio from the golden ratio, by strength.
Brine Calculator
Salt for a wet or dry brine, by weight of water or meat.
Meat Doneness Temperatures
USDA safe internal temperatures and steak doneness, °F and °C.
Ohm’s Law
Voltage, current, resistance, power.
Resistors (Series & Parallel)
Total resistance of resistors in series or parallel.
Resistor Color Code
Resistance and tolerance from the color bands.
Voltage Divider Calculator
Output voltage from two resistors in a divider.
LED Resistor Calculator
Series resistor value for an LED from supply and forward voltage.
Capacitor Energy Calculator
Energy and charge stored in a capacitor from capacitance and voltage.
RC Time Constant Calculator
Time constant τ = RC and the charge/discharge curve.
Capacitors in Series & Parallel
Total capacitance of capacitors wired in series or parallel.
Reactance Calculator
Capacitive and inductive reactance at a given frequency.
Battery Life Calculator
Estimate runtime from battery capacity and load current.
555 Timer Calculator
Frequency, duty cycle, and pulse width for a 555 from R and C.
Op-Amp Gain Calculator
Voltage gain, output, and clipping for the two basic op-amp configurations.
Filter Cutoff Frequency
Cutoff and resonant frequency for RC, RL, and LC filters.
AWG Wire Gauge
Diameter, area, resistance, and voltage drop for any AWG size.
Transformer Turns Ratio
Secondary voltage, current, and impedance ratio from the turns.
Power Dissipation
Heat dissipated in a component and the rating it needs.
Zener Regulator
Series resistor, zener current, and power ratings for a shunt regulator.
Inductor Energy
Energy stored in a coil, and the spike when current is interrupted.
Beam Deflection Calculator
Maximum deflection of a beam under a central or end point load.
Stress and Strain Calculator
Axial stress, strain, and elongation from force and dimensions.
Young’s Modulus Calculator
Elastic modulus from stress and strain, or axial deformation.
Torque to Power Calculator
Convert between torque, rotational speed (RPM), and power.
Gear Ratio Calculator
Gear ratio with output speed and torque from tooth counts.
Factor of Safety Calculator
Factor of safety from material strength and applied stress.
Reynolds Number Calculator
Reynolds number and flow regime — laminar, transitional, or turbulent.
Area Moment of Inertia Calculator
Second moment of area and section modulus for common beam cross-sections.
Beam Bending Stress Calculator
Maximum bending stress from the flexure formula σ = Mc/I.
Thermal Expansion Calculator
Linear thermal expansion ΔL = αL₀ΔT, with material coefficients.
Hoop Stress Calculator
Hoop and longitudinal stress in a thin-walled pressure vessel.
Flow Rate Calculator
Volumetric flow rate Q = Av and the continuity equation.
Euler Buckling
Critical buckling load, slenderness ratio, and critical stress for a column.
Heat Conduction
Heat flow, thermal resistance, and U-value through a material layer.
Torsional Stress
Shear stress and angle of twist in a solid or hollow shaft.
Bolt Torque
Tightening torque and clamp force for metric bolts by property class.
Pipe Pressure Drop
Friction head loss and pressure drop along a pipe run.
Belt & Pulley Calculator
Exact belt length, wrap angles, speed ratio and slip limit.
Note to Frequency Calculator
Frequency of any musical note, and the nearest note to a frequency.
Tempo to Delay Calculator
Delay and note-value times in milliseconds from a tempo in BPM.
Musical Interval Calculator
Frequency ratio and cents between two notes or a semitone count.
Audio File Size Calculator
Uncompressed audio file size from sample rate, bit depth, and length.
Harmonic Series Calculator
Overtone frequencies of the harmonic series from a fundamental.
Music Transposition Calculator
Transpose a note or key by a number of semitones.
Metronome
A free online metronome with adjustable BPM, time signature, and tap tempo.
Chord Finder
Find the notes in any chord from its root and quality — triads to 7ths and more.
Scale Finder
Find the notes of any scale or mode from its root — major, minor, modes, pentatonic.
Circle of Fifths
Key signatures, sharps and flats, and relative minors for all 12 keys.
Frequency to Note
Convert a frequency in Hz to the nearest note and cents deviation.
Decibel Calculator
Convert ratios to decibels and back, and add sound levels in dB.
Redshift to Velocity Calculator
Recession velocity from redshift z, low-z and relativistic.
Light Travel Time Calculator
How far light travels in a time, or how long it takes over a distance.
Stellar Parallax Calculator
Distance to a star from its parallax angle, in parsecs and light-years.
Schwarzschild Radius Calculator
Event-horizon radius of a black hole from its mass.
Surface Gravity Calculator
Surface gravity of a planet or star from its mass and radius.
Angular Size Calculator
Apparent angular size of an object from its size and distance.
Planet Weight Calculator
See what you would weigh on every planet, the Moon, and the Sun.
Moon Phase Calculator
Find the Moon phase and illumination for any date.
Wien’s Law Calculator
Convert between a blackbody’s temperature and its peak wavelength.
Hubble’s Law Calculator
Relate a galaxy’s recession velocity and distance with v = H₀d.
Telescope Magnification Calculator
Magnification, focal ratio, and exit pupil from your telescope and eyepiece.
Distance Modulus Calculator
Solve for distance, apparent, or absolute magnitude from the distance modulus.
Price Elasticity of Demand
Elasticity of demand from price and quantity, midpoint method.
Real GDP Calculator
Real GDP, nominal GDP, and the GDP deflator from any two.
CPI Inflation Rate Calculator
Inflation rate between two Consumer Price Index values.
Consumer & Producer Surplus
Consumer, producer, and total surplus from a linear market.
Comparative Advantage Calculator
Opportunity cost and comparative advantage for two producers.
Spending Multiplier Calculator
The multiplier and change in GDP from the marginal propensity to consume.
Unemployment Rate Calculator
Unemployment rate, labor-force participation, and employment-to-population ratio.
Quantity Theory of Money
Solve the equation of exchange MV = PQ for any variable.
Income & Cross-Price Elasticity
Income and cross-price elasticity of demand, with the good type classified.
Gini Coefficient Calculator
Income inequality from group income shares, with a Lorenz curve.
Deadweight Loss Calculator
Welfare loss from a per-unit tax, with a supply-and-demand diagram.
Fisher Equation Calculator
Real vs nominal interest rate and inflation — exact and approximate.
Marginal Analysis
MC, MR, average cost and the profit-maximising output from a schedule.
Profit Maximization
Solve MR = MC for quantity, price, profit, markup and elasticity.
Cobb–Douglas
Output, marginal products, factor shares and returns to scale.
Purchasing Power Parity
The rate prices imply, and how far the market departs from it.
Dosage Calculation
How much to give from the dose ordered and the strength on hand.
IV Drip Rate
Drops per minute for a gravity infusion from volume, time, and drop factor.
IV Flow Rate
Millilitres per hour to program into an infusion pump.
Infusion Time
How long a bag will take to run and when it finishes.
Weight-Based Dosage
Daily and per-dose amounts from a mg/kg order and body weight.
Paediatric Safe Dose
Check an ordered dose against the safe mg/kg/day range.
Reconstitution
Concentration after adding diluent, and the volume to draw up.
Heparin Drip Rate
Bolus, units per hour, and pump rate for a weight-based heparin order.
Creatinine Clearance
Estimate CrCl in mL/min for renal dose adjustment.
eGFR Calculator
Estimated GFR and CKD stage from serum creatinine.
Anion Gap
Serum anion gap, with or without potassium, corrected for albumin.
Corrected Sodium
Adjust measured sodium for a raised glucose — Katz and Hillier.
Corrected Calcium
Albumin-corrected serum calcium in mg/dL or mmol/L.
mEq ↔ mmol ↔ mg
Convert electrolyte amounts using molar mass and valence.
Mean Arterial Pressure
MAP from systolic and diastolic, with pulse pressure.
Glasgow Coma Scale
Score eye, verbal and motor response out of 15.
Apgar Score
Score the five newborn signs at 1 and 5 minutes.
Parkland Formula
Burn fluid for the first 24 hours, with a Rule of Nines helper.