HesapHanem

Frequency to Note Calculator

Identify the musical note closest to a frequency.

How it is calculated

The tool converts a frequency to a MIDI-style note number, rounds to the nearest semitone, then measures how far off you are: n = round(12 × log2(f ÷ A4)) + 69, exact = A4 × 2(n − 69) ÷ 12, cents = 1200 × log2(f ÷ exact). Here f is the frequency in hertz and A4 is the reference tuning for the A above middle C (440 Hz by default; it falls back to 440 if empty or not positive). The note name uses sharps and its octave number, with C4 as middle C. One semitone is 100 cents, so the deviation is between −50 and +50 cents. A plus sign means sharp and a minus sign means flat. The scale is equal temperament.

Worked example

Measure a string at 446 Hz with A4 set to 440 Hz. Distance from A4: 12 × log2(446 ÷ 440) ≈ 0.23 semitones, which rounds to 0, so the nearest note is A4 (note number 69). Its exact pitch is 440.00 Hz. Deviation: 1200 × log2(446 ÷ 440) ≈ +23.45 cents. The tool reads A4, +23.45 ¢, so the string is about a quarter of a semitone sharp.

Try this example →

Common mistakes

  • Leaving the reference tuning at 440 when the ensemble tunes to 442 or another pitch. All cents readings shift accordingly.
  • Reading cents as hertz. A deviation of +23 cents is a small fraction of a semitone, not 23 Hz.
  • Confusing octave numbers. Middle C is C4 and the A above it is A4; some software labels the same pitch as C3 or C5.
  • Feeding a harmonic or overtone instead of the fundamental. A guitar string's second harmonic reads one octave too high.
  • Expecting flats. The tool names notes with sharps, so B♭ appears as A#.

About this calculator

This calculator finds the nearest musical note to any frequency and its deviation in cents (hundredths of a semitone) from that note's standard pitch, based on an adjustable A4 reference tuning (commonly 440 Hz, but concert pitches vary). It uses the equal-tempered scale formula, where each semitone is a factor of the 12th root of 2 apart in frequency.

Musicians, piano and instrument tuners, and audio engineers use it to identify what note a recorded or measured frequency corresponds to, and to see exactly how sharp or flat an instrument is in cents when tuning by ear or with test tones.

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Comments (1)

  • Editorial team

    If you read frequencies off a spectrum analyser or tuner app, enter the lowest strong peak, since that is normally the fundamental. As a check, 82.41 Hz returns E2, the low string of a standard guitar, with a deviation near zero. A reading such as 70 Hz comes out as C#2 at about +17.5 cents, which tells you it sits between notes rather than on one. Which instrument are you tuning, and does it use a reference other than 440?

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