Note / Frequency / MIDI Converter
Type in any one of the three — a note name (like A4 or F#3), a MIDI number (0–127), or a frequency in Hz — and the others update instantly. Uses middle C = C4 = MIDI 60. Change the tuning reference for A=432 and friends.
Want every note at once? See the full note / MIDI / frequency chart.
How it works
Equal temperament divides the octave into twelve equal ratios, so frequency is exponential in pitch. Everything is anchored to A4 = 440 Hz, which is MIDI note 69.
frequency = 440 × 2 ^ ((midi_note - 69) / 12)
midi_note = 69 + 12 × log2(frequency / 440)The twelfth root of two — about 1.05946 — is the ratio between any two adjacent semitones.
Worked example
- MIDI 69 (A4) = 440 × 2^0 = 440.00 Hz
- MIDI 81 (A5) = 440 × 2^1 = 880.00 Hz — one octave up doubles the frequency
- MIDI 57 (A3) = 440 × 2^-1 = 220.00 Hz
- MIDI 60 (C4) = 440 × 2^(-9/12) = 261.63 Hz
In practice
- Octaves double. If you know one frequency you know every octave of it, which is often faster than reaching for a calculator.
- EQ by note. Converting the fundamental of a bass part to Hz tells you where to cut or boost, instead of sweeping blindly.
- Kick and bass collisions usually happen because their fundamentals are within a couple of semitones. Working out both frequencies makes the fix obvious.
- A = 432 Hz appears often online. It is a different reference pitch, not a different tuning system — every relationship stays the same, everything just shifts down about 32 cents.
- Cents are hundredths of a semitone: 100 cents is a semitone, so a ratio of 2^(1/1200) per cent.