Convert between MIDI numbers, note names and frequencies
| MIDI | Note | Freq (Hz) | Octave | Instruments |
|---|
MIDI (Musical Instrument Digital Interface) is a protocol developed in 1983 that allows electronic instruments, computers, and software to communicate. Rather than transmitting audio, MIDI transmits instructions — which note to play, how loud, how long, and on which channel.
Notes in MIDI are represented as numbers from 0 to 127 — a total of 128 possible pitches spanning over ten octaves. Each number maps to a specific pitch: MIDI 69 is A4, the concert A at 440 Hz. Every semitone step corresponds to one MIDI number, and every octave spans exactly 12 numbers.
The frequency of any MIDI note can be calculated with the formula: frequency = 440 × 2^((midi − 69) / 12). This is why each octave doubles the frequency — A3 is 220 Hz, A4 is 440 Hz, A5 is 880 Hz.
| MIDI | Note | Frequency | Significance |
|---|---|---|---|
| 0 | C-1 | 8.18 Hz | Lowest MIDI note (below human hearing range) |
| 21 | A0 | 27.50 Hz | Lowest key on a standard 88-key piano |
| 36 | C2 | 65.41 Hz | Typical bass guitar low E (open string = E1, 41 Hz) |
| 60 | C4 | 261.63 Hz | Middle C — the central reference note |
| 69 | A4 | 440.00 Hz | Concert A — the international tuning standard |
| 72 | C5 | 523.25 Hz | One octave above middle C |
| 108 | C8 | 4186.01 Hz | Highest key on a standard 88-key piano |
| 127 | G9 | 12,543.85 Hz | Highest MIDI note |
Different instruments can only play certain notes. These ranges determine which MIDI notes will produce a realistic sound from a given instrument — notes outside the range may be silent, transposed, or produce an unnatural timbre in a virtual instrument.
| Instrument | Low note | High note | MIDI range |
|---|---|---|---|
| Piano (88-key) | A0 (27.5 Hz) | C8 (4186 Hz) | 21 – 108 |
| Guitar (standard) | E2 (82.4 Hz) | E6 (1319 Hz) | 40 – 88 |
| Bass guitar | E1 (41.2 Hz) | C4 (262 Hz) | 28 – 60 |
| Violin | G3 (196 Hz) | B7 (3951 Hz) | 55 – 103 |
| Human voice (avg) | C3 (131 Hz) | C6 (1047 Hz) | 48 – 84 |
| Trumpet | E3 (165 Hz) | Bb5 (932 Hz) | 52 – 82 |
| Flute | C4 (262 Hz) | D7 (2349 Hz) | 60 – 98 |
Look up any MIDI note number (0–127) to see the note name, octave, frequency in Hz, and acoustic wavelength. Reverse lookup converts note names (C4, A#3, Bb5) to MIDI numbers. Instrument range badges show which standard instruments can play each note. The full 128-note reference table is scrollable and clickable. Use the Play tone button to hear the note via the Web Audio API.