Reference
Interactive references — periodic table, formulas, constants, and lookups.
42 tools
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.
About reference tools
Fast, interactive references you can keep open in a tab while you study.
When to use these tools
Common reference tasks and the tool that handles each one.
Frequently asked questions
Common questions about reference — the concepts behind the tools above.