MIDI Note to Frequency Converter
Convert a MIDI note number (0–127) to its frequency in Hz using equal temperament with an adjustable A4 reference. Shows the note name and octave. Runs in your browser.
In 12-tone equal temperament, frequency = A4 × 2^((MIDI − 69) ÷ 12). MIDI 69 is A4 (440 Hz by default), and every 12 MIDI numbers is one octave (a doubling of frequency). MIDI 60 is middle C (C4 ≈ 261.63 Hz). Raising the A4 reference (e.g. 442 Hz) shifts every note proportionally. Everything runs in your browser.
About this tool
MIDI represents musical pitch as integers from 0 to 127 rather than frequencies — note number 60 is middle C, 69 is the A above it, and each step of one represents one semitone. To turn a MIDI note into an actual sound, synthesizers and audio software convert that number to a frequency in hertz, and this tool does the same conversion. It uses the standard equal-temperament formula frequency = A4 × 2^((MIDI − 69) ÷ 12), anchored to the reference note A4 = MIDI 69 = 440 Hz by default. The structure of the formula reflects how pitch works: because the exponent divides by 12, every increase of 12 in the MIDI number doubles the frequency — exactly one octave — and each single semitone multiplies the frequency by the twelfth root of two (about 1.0595). So MIDI 60 (middle C) comes out to roughly 261.63 Hz, MIDI 69 to exactly 440 Hz, and MIDI 81 (the A an octave up) to 880 Hz. The A4 reference is adjustable because tuning standards vary: many orchestras tune to 442 or 443 Hz, and historically informed performance often uses 415 Hz; changing it shifts every note's frequency proportionally. The full MIDI range spans from note 0 (about 8.18 Hz, below human hearing) to 127 (about 12.5 kHz), covering far more than any acoustic instrument. This conversion is the foundation of how digital instruments generate pitch, how tuners map notes, and how software synthesizers turn a sequence of MIDI numbers into audible tones. It is the exact inverse of converting a measured frequency back to the nearest note. Everything runs in your browser; nothing is uploaded.
How to use it
- Drag the slider or type a MIDI note number from 0 to 127.
- Adjust the A4 reference if you tune to something other than 440 Hz.
- Read the resulting frequency in Hz along with the note name and octave.
- Copy the value for use in a synth, tuner, or audio code.
Frequently asked questions
- How do you convert a MIDI note to frequency?
- Use frequency = 440 × 2^((MIDI − 69) ÷ 12) for standard tuning. MIDI 69 is A4 = 440 Hz, and each 12 MIDI numbers is one octave (a doubling of frequency).
- What frequency is MIDI note 60?
- MIDI 60 is middle C (C4), about 261.63 Hz at A4 = 440 Hz. MIDI 69 is A4 = 440 Hz exactly, and MIDI 72 is C5 ≈ 523.25 Hz.
- What is the range of MIDI note frequencies?
- MIDI 0 is about 8.18 Hz (below hearing) and MIDI 127 is about 12,543 Hz, spanning far more than any single acoustic instrument. Middle C (60) and A440 (69) sit in the middle.
- Why can I change the A4 reference?
- Tuning standards differ: 440 Hz is the international standard, but orchestras often use 442–443 Hz and Baroque ensembles 415 Hz. Adjusting A4 rescales every note frequency proportionally.
- What tuning system does this use?
- 12-tone equal temperament, where each semitone is the twelfth root of two apart. This is standard for synthesizers and most modern music. Other tunings (just intonation) would give slightly different frequencies for some notes.
- Is anything uploaded?
- No. The conversion runs entirely in your browser.