Frequency to Note Converter (and Back)
This frequency to note converter turns any frequency in hertz into the nearest note, the deviation in cents and the MIDI number, or a note into its frequency. The reference pitch A4 is adjustable.
Example: Conversion: Frequency to note · Frequency 330 Hz · Reference pitch A4 440 Hz → Result: E4 (+2 cents). Source: Wikipedia – Piano key frequencies (f(n) = 2^((n − 49)/12) · 440 Hz, MIDI numbers). Updated: .
How it is calculated
440 Hz is the note A4 (MIDI 69), and every doubling of the frequency is one octave higher. The converter assigns every frequency to the nearest note in equal temperament and shows how many cents it is off.
How it is calculated
The note number follows from MIDI = 69 + 12 · log₂(f / 440 Hz). Rounded, that is the nearest key; the remainder times 100 gives the cents. In reverse, f = 440 Hz · 2^((MIDI − 69) / 12). A semitone is a factor of 1.0595, 100 cents make a semitone and 1,200 cents an octave.
What it is useful for
- Tuning a guitar, piano or voice: check the distance to the target note in cents with a frequency meter.
- Setting synthesizers and tone generators to a specific note.
- Matching tones from measurements or spectra (FFT) to a note.
Frequently asked questions
What frequency is the note A4?
By default 440 Hz. This is concert pitch, which tuners and most instruments follow; many orchestras tune to 442 Hz.
How do you convert a frequency to a note?
Use MIDI = 69 + 12 · log₂(f / 440). Round the result to a whole number to get the note. The difference times 100 is the deviation in cents.
What are cents in tuning?
A cent is one hundredth of a semitone. Most people cannot hear a difference to the target note below about 5 cents.
What is the frequency of middle C?
Middle C (C4, MIDI 60) is about 261.63 Hz when A4 is tuned to 440 Hz.
Sources and legal basis
As of: · Editorial policy
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