Note Frequency Calculator
Frequency to note, note to frequency, with cents.
Work out Note Frequency. Frequency to note, note to frequency, with cents. Shows the working, not just the answer.
Nearest note
A4
440 Hz · In tune
Equal temperament divides the octave into twelve equal ratios of the twelfth root of two. That makes every key equally usable and every interval except the octave very slightly out of tune against the pure whole-number ratios the ear expects — a deliberate trade that replaced systems where a few keys sounded perfect and the rest were unplayable. Cents measure the error: a hundred to a semitone, and about five before most listeners notice on a sustained note. The tuning reference is not universal. A4 = 440 Hz is the modern standard, many European orchestras play at 442 or 443, and historically informed performance often uses 415 — a full semitone below, which is why baroque recordings can sound like they are in a different key.
How the Note Frequency Calculator works
Convert between frequency, note name and MIDI number, with the tuning error in cents and the wavelength in air. The A4 reference is adjustable, because 440 Hz is standard but far from universal — orchestras play at 442 and baroque ensembles at 415.
Also known as: what note is 440 hz · hz to note converter · midi note number to frequency · how many cents out of tune
Frequently asked questions
What frequency is A4?
440 Hz by the modern standard. Many European orchestras tune to 442 or 443 for brightness, and historically informed baroque performance commonly uses 415 — almost exactly a semitone lower.
What is equal temperament?
Dividing the octave into twelve equal frequency ratios of the twelfth root of two. Every key becomes equally usable at the cost of every interval except the octave being slightly out of tune against pure whole-number ratios.
What is a cent?
One hundredth of a semitone. Around five cents is where most listeners start to notice a sustained note is off, though the threshold is much tighter for two notes sounding together, where beating gives it away.
How do I convert a MIDI note number to a frequency?
MIDI 69 is A4. Every step of one is a semitone, so the frequency is the reference times two to the power of the semitone difference over twelve. MIDI 60 — middle C — works out at 261.63 Hz.
Why does the same note sound different on different instruments?
Because the fundamental frequency is only part of it. The pattern of harmonics above the fundamental, and how they change over the note's duration, is what the ear reads as the instrument.
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