Musical pitch converter
Convert frequencies to MIDI note numbers and semitones from concert A, the maths behind every tuner and synthesiser.
That's about the same as concert A. That is about 0 semitones from concert A.
What it means
What does that sound like?
Based on equal temperament with A4 at 440 Hz. Orchestras sometimes tune to 442 or 443, shifting everything slightly.
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Three things worth knowing
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An octave doubles
A440 up an octave is 880 Hz, down an octave is 220. Each semitone multiplies by the twelfth root of two, about 1.0595.
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A440 is younger than you think
Concert pitch drifted for centuries; Handel’s A was around 423 Hz. The 440 standard was only agreed internationally in 1955.
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Semitones are not equal in hertz
A semitone near A440 is 26 Hz wide; an octave lower it is 13 Hz. Tuning by a fixed number of hertz goes out of tune as you climb.
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Background
About pitch units
Pitch is logarithmic: every octave doubles the frequency, and every octave holds 12 semitones. MIDI note 69 is A440, and each step of one is a semitone.
The formula is f = 440 × 2^((note − 69) ÷ 12).