How is the nearest note calculated?

The converter uses the equal-temperament formula n = 69 + 12 · log2(f / A4), which gives a fractional MIDI value. Rounding to the nearest whole number identifies the closest note, and the fractional part times 100 gives the cents deviation. A4 = MIDI 69, defaulting to 440 Hz.

What does the cents value mean?

A cent is one hundredth of an equal-tempered semitone. A reading of +12 cents means the frequency is 12 cents sharp of the nearest note; −12 means flat. Most listeners detect pitch errors above about 5 to 10 cents, so anything within ±5 is effectively in tune.

Why can I change the A4 reference?

Standard tuning fixes A4 at 440 Hz, but orchestras and historical instruments sometimes use 432, 442 or 415 Hz. Changing the reference shifts every note proportionally, so the same input frequency maps to a different note name or cents value depending on the chosen tuning.

What octave numbering does it use?

It uses scientific pitch notation where middle C is C4 and A4 is 440 Hz. This matches MIDI convention with C-1 as MIDI 0. Note that some software labels middle C as C3 or C5 — the frequency is identical, only the octave label differs.

Can it identify any frequency, even between notes?

Yes. Every positive frequency maps to a nearest note plus a cents offset. A frequency exactly between two notes will round to whichever is closer and show a cents value near ±50. This makes the tool useful for analysing slightly out-of-tune instruments or non-musical tones.

Hz to Musical Note Converter

Every audible frequency corresponds to a musical pitch — exactly on a note or some number of cents away from it. This converter takes a frequency in Hz and tells you the nearest equal-temperament note, its octave, its MIDI number, and precisely how sharp or flat the input is.

How it works

Equal temperament divides each octave into twelve equal semitones. The position of any frequency on the MIDI scale is:

n = 69 + 12 · log2(f / A4)

where A4 is the reference pitch (440 Hz by default, mapped to MIDI 69). Rounding n to the nearest integer gives the closest note. The leftover fraction, multiplied by 100, is the deviation in cents:

cents = (n − round(n)) · 100

The exact frequency of that nearest note is recovered with A4 · 2^((round(n) − 69) / 12), which the tool also displays so you can see your target.

Tips and example

A reading of 445 Hz with A4 set to 440 returns A4 at about +19.6 cents — noticeably sharp. Drop the reference to 442 Hz and the same 445 Hz reads only +11.7 cents, because the whole scale has shifted up.

Use the cents value to decide which way to tune: positive means lower the pitch.
Within ±5 cents is generally heard as in tune.
Match the A4 reference to your ensemble before trusting the note name near octave edges.

The conversion runs entirely in your browser.