AUDIO
Note Frequency Calculator
Convert MIDI notes to frequency (Hz) and back, with cents offset.
PITCH REFERENCE
Note and frequency conversion
Note frequency guide
Every musical note is a specific frequency: A4 rings at 440 Hz, the note above it (A#4) at roughly 466 Hz, and so on across the 12-note scale. This calculator converts between note names/MIDI numbers and frequencies in both directions, with fine-tuning in cents — the tool of choice for game audio, music programming, and synth design.
It runs entirely in your browser with the standard A4 = 440 Hz tuning.
The math: equal temperament in one formula
Western music divides each octave into 12 equal steps, so each semitone is a factor of 2^(1/12) above the previous one. That yields the formula: f = 440 × 2^((midi − 69) / 12), where MIDI 69 is A4 and 440 Hz is its frequency.
The calculator applies exactly this — with cents (hundredths of a semitone) as a fine-tuning offset, the same unit synth and DAW software use for micro-tuning.
MIDI numbers, demystified
MIDI represents every playable note as a number from 0 to 127: MIDI 60 is middle C, 69 is A4, and every +12 is one octave up. Game engines and audio libraries use MIDI numbers everywhere — spawning a note is often just passing a number.
This calculator shows the note name (C4, A#3…) for any MIDI number, so you never have to count semitones by hand again.
Where game audio uses this
- Procedural audio — generating tones at exact frequencies for SFX, ambient drones, or UI blips.
- Pitch mapping — converting a game parameter (speed, height) into a note via MIDI.
- Tuning verification — checking that a sampled instrument is at concert pitch.
- Synth design — setting oscillator frequencies precisely to match musical material.
- Level design references — A4 = 440 Hz is also a calibration reference for audio hardware.
Tip: For a quick reference: middle C (MIDI 60) is 261.63 Hz, and A4 (MIDI 69) is 440 Hz. Every octave up doubles the frequency.
Frequently asked questions
What frequency is A4?
A4 is 440 Hz by standard tuning (A440). This calculator uses that convention, which is universal in modern music.
What is MIDI note 60?
Middle C (C4) — the reference point in MIDI numbering. MIDI numbers go from 0 (C-1) to 127 (G9).
How do I convert Hz to a note?
Use the Hz → Note mode: enter the frequency and it returns the nearest note name, MIDI number, and cents offset.
What are cents?
Cents are hundredths of a semitone — 100 cents = one semitone. They are used for fine tuning (e.g. a note 15 cents flat).
Why do frequencies double per octave?
An octave is a 2:1 frequency ratio by definition — a note one octave higher vibrates twice as fast. The 12 semitones in between are spaced geometrically (×2^(1/12) each).
Privacy note: note and frequency calculations happen in your browser. Nothing is uploaded.