Note ↔ Frequency ↔ MIDI Converter
Any note, frequency or MIDI number to the other two — with cents, tuning and a piano table
How it works
Type a note (A4, C#3, B♭2), a frequency in hertz, or a MIDI number; the other two update, and a frequency that falls between notes shows how many cents sharp or flat it is. Equal temperament is assumed: f = A4 × 2^((midi − 69) / 12). Change A4 to 432, 442 or any value to retune everything, switch between sharps and flats, hear the pitch with the Play button, and scroll the 88-key table.
Questions
What frequency is middle C?
C4, MIDI 60, is 261.63 Hz at A4 = 440 Hz. A4 itself is MIDI 69.
How do I convert a frequency to a MIDI note?
midi = 69 + 12 × log2(f / 440). Round to the nearest whole number for the note; the fraction × 100 is the deviation in cents.
What does 432 Hz change?
Every note drops by about 32 cents (≈1.8%). Set A4 = 432 to see the exact frequencies.