What does a negative cents offset mean?

That the measured pitch is below the nearest note. The sign is the direction and the magnitude is how far, so minus twenty cents describes a pitch a fifth of a semitone flat. When the reading is close enough that the sign is the only difference, the pitch is effectively in tune.

Why does the note name change when I move the reference?

Because the reference defines what each note is. A pitch that reads as a sharp note at the modern tuning may read as the note below if the reference is lowered far enough, since the whole set of note frequencies moves with it. Choosing the reference that matches the material is what makes the reading meaningful.

How many cents off is audible?

It depends on the material and the listener, but sustained tones start to sound out of tune from roughly five cents and become clearly wrong by about twenty. The panel highlights readings inside five cents for that reason, and it is a reasonable working threshold for tuning by ear.

What is the fractional note number for?

It places the pitch between notes on the same scale that a synthesizer or sequencer uses, so a value of sixty nine point five is exactly halfway between A4 and the note above. For a pitch that needs to be reproduced rather than named, that figure is more useful than the cents offset.

Can it tell me which note a recording is in?

Only one pitch at a time, and only if you already have a frequency for it. Identifying the key of a piece comes from the notes it uses rather than from a single measurement, and the note can then be confirmed with the note frequency calculator or the interval calculator.

Frequency to MIDI Note

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Frequency to MIDI Note names the note nearest a measured frequency and says how far off it is, in cents and as a fractional note number. It is the tool for making sense of a pitch reading.

What is Frequency to MIDI Note?

Enter a frequency and the panel gives the nearest note, its note number, the offset in cents and the exact fractional position.

The inputs and the four results:

A frequency field from a tenth of a hertz to twenty five thousand, defaulting to four hundred and fifty.
A tuning reference slider for the note A4 from four hundred and fifteen to four hundred and sixty six hertz.
A nearest note name and its whole note number.
A signed offset in cents, highlighted when the reading is within five cents of the note.
The exact fractional note number, to two decimal places, which is the position between notes that a synthesizer would need.

The calculation is the inverse of the note-number conversion. A frequency is measured, the reference is applied to bring it into the standard relationship, and the logarithm of the ratio to the reference is taken in base two and scaled by twelve, since there are twelve equal semitones in an octave. The integer part of that result names the nearest note and the fraction is how far the pitch sits between notes; multiplying the fraction by a hundred gives cents, a hundred of which make a semitone. The cents figure is the one that matters for tuning, because it is the same proportional distance at every pitch: a reading twenty cents sharp is a fifth of the way to the next note whether the note is low or high, whereas the same number of hertz would be a wide interval in the bass and a negligible one at the top. That is why the panel highlights a reading within five cents, which is roughly the point at which a sustained tone starts to sound out of tune to a listener. The reference slider matters because it changes what counts as the note. A reading taken from an instrument tuned to an older pitch will report a different note and offset if the reference is left at the modern figure, so the honest reading requires the reference to match the material. Every result here is derived from arithmetic on the number entered rather than from any audio, and it is exact.

What it does not cover:

No pitch detection, so the frequency has to come from a tuner or a meter.
Equal temperament only, so a differently tempered instrument reads as a series of detunings.
No ambiguity resolution, so a pitch close to midway between two notes is reported as whichever is nearer.
Nothing about vibrato or a pitch that moves over time.
No instrument transposition for written notes.
Nothing is uploaded, and no history is kept.

Use it when a measured frequency has to become a note name and a tuning error, which is how a strobe reading or a spectrum peak is usually interpreted. When the direction is a note number that has to become a frequency, the MIDI note to frequency tool does that, and when the input is a note name rather than a number, the note frequency calculator accepts names as written.

How to use Frequency to MIDI Note

Enter the measured frequency in hertz.
Set the tuning reference to match the instrument or recording.
Read the nearest note and the signed offset in cents.
Use the fractional note number if the pitch has to be placed in software.

When to use Frequency to MIDI Note vs related tools

Frequency to MIDI Note is the interpretation step for any pitch measurement, turning a number in hertz into a note and a tuning error. MIDI Note to Frequency converts the other way from a note number. Note Frequency Calculator combines both directions and also accepts written note names, and Guitar Tuner or Instrument Tuner produce the frequency reading in the first place.

Privacy & Security

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