HesapHanem

Musical Note Frequency Calculator

Find the exact pitch in hertz for any note and octave.

How it is calculated

The tool uses equal temperament. Each note gets a MIDI number m = (octave + 1) × 12 + semitone offset, where C = 0, C# = 1 … B = 11, so A4 is 69. The frequency is f = tuning × 2^((m - 69) / 12), with the reference pitch for A4 (default 440 Hz; a value of zero or less falls back to 440). Every semitone multiplies the frequency by about 1.0595, and each octave doubles it. The tool also gives the wavelength in air as 343 / f metres, which assumes sound travels at 343 m/s (air at about 20 °C). Results are rounded to two decimals.

Worked example

Middle C is note C in octave 4 with A4 = 440 Hz. MIDI number = (4 + 1) × 12 + 0 = 60. That is 9 semitones below A4 (69 - 60 = 9). Frequency = 440 × 2^(-9/12) = 440 × 0.5946 = 261.63 Hz. Wavelength = 343 / 261.63 = 1.31 m. The MIDI number shown is 60.

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Common mistakes

  • Using a different octave numbering. Here octave 4 holds middle C and A4 = 440 Hz; some software calls middle C C3.
  • Thinking D# and E-flat give different results. Both are the same pitch in equal temperament, so pick the sharp name.
  • Entering the tuning reference for the wrong note: it is the frequency of A4, not of the note you are looking up.
  • Expecting a historical or just-intonation value; the tool gives only equal temperament.

About this calculator

This calculator finds the frequency in hertz of a musical note under 12-tone equal temperament: f = A4 × 2^((n−69)/12), where n is the note's MIDI number and A4 is the reference tuning pitch (usually 440 Hz, though orchestras sometimes tune to 442 Hz or other values). Each semitone step multiplies or divides the frequency by the twelfth root of two.

Musicians, piano tuners, instrument builders, and audio/synth developers use it to look up the exact pitch of any note and octave, verify a tuner's readings, or generate reference tones for software synthesizers.

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Comments (1)

  • Editorial team

    The wavelength line shows why low notes behave differently in a room: bass guitar E1 is 41.20 Hz with a wavelength of 8.33 m, longer than many rooms. For period instruments, change the A4 reference: 415 Hz sits about a semitone below 440 Hz, so every note shifts down together. Octave numbers follow the scientific convention, where middle C is C4. Which instrument or tuning are you working with?

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