Frequency to Note Calculator
Find the nearest musical note for any frequency in Hz. Shows the note name, octave, MIDI number, and how many cents sharp or flat you are.
How to use this tool
- Enter frequency in the fields above.
- Results update instantly as you type — or click Calculate.
- Read your nearest note and the full breakdown beneath it.
Identify the nearest musical note for any Hz frequency and see how many cents off pitch it is.
Formula
MIDI (exact) = 69 + 12 × log2(freq ÷ 440)
Nearest MIDI = round(MIDI exact)
Cents offset = (MIDI exact − nearest MIDI) × 100
Ideal frequency = 440 × 2(nearest MIDI − 69) ÷ 12
How it works
This calculator identifies the closest equal-tempered musical note to any input frequency by inverting the standard A4=440 Hz tuning formula via a base-2 logarithm. The exact (non-integer) MIDI value is rounded to the nearest semitone, and the fractional remainder is converted to cents (hundredths of a semitone) to show how far sharp or flat the input is. It assumes 12-tone equal temperament; microtonal or just-intonation pitches will report a non-zero cents offset.
Worked example
Worked example
- Frequency = 440 Hz.
- MIDI exact = 69 + 12 × log₂(440 ÷ 440) = 69 + 12 × 0 = 69.0.
- Nearest MIDI = round(69.0) = 69.
- Cents offset = (69.0 − 69) × 100 = 0 ¢.
- Note name: MIDI 69 → A, octave = floor(69/12) − 1 = 4 → A4.
- Ideal frequency = 440 × 2^0 = 440 Hz.
440 Hz = A4, MIDI 69, 0 ¢ offset, ideal frequency 440 Hz.
Key terms
- Cents
- A unit of pitch equal to 1/100 of a semitone. A perfect semitone = 100 ¢; an octave = 1200 ¢. Used to express small tuning deviations.
- Nearest note
- The equal-tempered pitch whose frequency is closest to the input, determined by rounding the exact MIDI value.
- Cents offset
- How many cents the input frequency sits above (+) or below (−) the ideal equal-tempered pitch. 0 ¢ means perfectly in tune.
- Ideal frequency
- The mathematically exact frequency of the nearest equal-tempered note, computed from its MIDI number.
- Base-2 logarithm (log₂)
- The inverse of the octave doubling relationship. log₂(2) = 1 corresponds to one octave = 12 semitones.
Frequently asked questions
- What note is 432 Hz?
- 432 Hz is A4 minus about 31.77 cents — roughly a third of a semitone below A440.
- What does cents offset mean?
- One semitone = 100 cents. A positive offset means the frequency is sharp; negative means flat.