Convert between MIDI note numbers, note names and frequencies in Hz, see the cents offset, and play the resulting tone.
| Note | Frequency |
|---|
This tool uses the standard MIDI tuning convention: MIDI note 69 is defined as A4, tuned to 440Hz, and every other note's frequency is derived from that fixed reference using the equal-temperament formula 440 × 2^((midi − 69) / 12). Typing a MIDI number computes its frequency directly. Typing a frequency instead runs the formula in reverse with a base-2 logarithm to find the nearest MIDI note, then reports how far off in cents (hundredths of a semitone) your typed frequency is from that note's exact pitch.
Every semitone is the same ratio apart on a logarithmic scale, which is how nearly all modern instruments and software are tuned.
A4 = 440Hz and MIDI note 69 is the fixed anchor point every other frequency is calculated from.
100 cents make up one semitone, so the cents readout shows exactly how sharp or flat an arbitrary frequency is.
The reference table below is generated from the same formula for every key from A0 (MIDI 21) to C8 (MIDI 108).
MIDI note 69 is defined as A4, and 440Hz (A440) is the internationally standard tuning reference for the A above middle C. Every other note's frequency is calculated as a number of semitones above or below that fixed point.
Under this tool's convention, middle C is MIDI note 60, labeled C4. Some software uses a different octave-numbering offset, so you may occasionally see middle C labeled C5 elsewhere — the underlying MIDI number, 60, stays the same either way.
A cent is one hundredth of a semitone. When you type a frequency that doesn't land exactly on a note, the tool rounds to the nearest MIDI note and shows how many cents sharp (positive) or flat (negative) your frequency is from that note.
Using the equal-temperament formula frequency = 440 × 2^((midi − 69) / 12), which spaces every semitone evenly on a logarithmic scale.
No. It generates a simple sine wave locally using the Web Audio API's oscillator node — no audio files or network requests are involved.
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