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Music & Audio

Music and audio math — note frequencies, tempo delays, intervals, and sample sizes.

6 tools

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.

About music & audio tools

The math behind music and audio — note-to-frequency (A4 = 440 Hz, 12-tone equal temperament), tempo-to-delay times, interval ratios and cents, the harmonic series, sample-size estimates, and transposition. Each tool shows the formula and the working, for producers, students, and instrument builders.

When to use these tools

Common music & audio tasks and the tool that handles each one.

Frequently asked questions

Common questions about music & audio — the concepts behind the tools above.

Why is A4 tuned to 440 Hz?
A4 — the A above middle C — is the standard reference pitch that most instruments tune to, and 440 Hz is its internationally recognized value (standardized by ISO 16). Every other note’s frequency is derived from it, though some orchestras deliberately tune slightly higher, such as 442 or 443 Hz.
Why does an octave double the frequency?
An octave is defined by a 2:1 frequency ratio: the note one octave above another vibrates exactly twice as fast. Our ears perceive that doubling as “the same note, higher,” which is why A5 (880 Hz) sounds like A4 (440 Hz) raised by an octave.
How do you convert tempo (BPM) to a delay time?
One beat lasts 60,000 divided by the tempo in beats per minute, in milliseconds. So at 120 BPM a quarter-note delay is 500 ms; halve it for eighth notes (250 ms) or quarter it for sixteenths (125 ms) to sync effects to the beat.
What is a semitone and how do intervals relate to it?
A semitone is the smallest step in standard Western tuning — one fret on a guitar or one key (including black keys) on a piano. Intervals are measured in semitones: a major third is 4, a perfect fifth is 7, and a full octave is 12.

Other subjects

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