0
0
Type a note such as A4, C#3 or Bb2 to get its frequency and MIDI number, add a cents offset for detuned pitches, enter any frequency to find the nearest note and how many cents sharp or flat it is, or enter a MIDI number from 0 to 127. Change the A4 reference to work at 432 Hz, 442 Hz or any tuning, and open the chart for every piano key at once.
Middle C (C4, MIDI 60) is 261.63 Hz when A4 is tuned to 440 Hz.
A4 at 440 Hz is MIDI note 69. Each semitone up adds one to the MIDI number, and each octave adds 12.
MIDI = 69 + 12 × log2(frequency ÷ 440). The whole number is the nearest note, and the fraction times 100 is how many cents it is sharp or flat.
A cent is one hundredth of a semitone, so an octave has 1200 cents. Most people notice tuning differences of about 5 to 10 cents.
There are two naming conventions. This tool uses C4 = MIDI 60, while Ableton, FL Studio and some other DAWs label the same note C3. The MIDI number and frequency are identical.