Why does the tuning reference move every note?

Because equal temperament defines every note as a ratio relative to the reference rather than as an absolute frequency. Changing A4 therefore changes the whole set proportionally: the notes far from A move by more hertz than the ones near it, which is why the reference shifts the scale rather than transposing it.

What does the cents figure mean?

It is the distance from the nearest note measured in hundredths of a semitone. A reading of twenty cents sharp means the pitch is a fifth of the way to the note above it, and it is the unit that matters in tuning because it is the same size at every pitch.

What is scientific pitch notation?

The system where a letter and an accidental are followed by an octave number, with middle C written C4 and the A above it A4. The octave number increments at C, not at A, which is the detail that most often trips people up when typing a note in.

Can it handle double sharps or flats?

The parser accepts a letter with a sharp or flat and an octave number, which covers ordinary naming. A double accidental is better written as the equivalent single name, since the pitch is the same and the conversion is concerned with pitch rather than with spelling.

Why is the MIDI number not a whole number?

Because the frequency you entered falls between two notes. The integer part identifies the nearest note and the fraction gives the detuning, so a value of sixty point two means a note slightly sharp of middle C. The same information appears in the cents column with a sign.

Note Frequency Calculator

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Note Frequency Calculator converts between note names and frequencies in both directions, and it can do it against a tuning reference other than the modern standard. Type a note to get its frequency, or a frequency to get the nearest note and how far off it is.

What is Note Frequency Calculator?

Set the tuning reference, then use either panel: a note name gives a frequency, or a frequency gives a note with its offset in cents.

The controls and the two panels:

A tuning reference from four hundred and fifteen to four hundred and sixty six hertz for the note A4, defaulting to the modern four hundred and forty.
A note field accepting scientific pitch notation such as A4, C sharp 3 or E flat 2, with the resulting frequency and the MIDI number beneath it.
A frequency field from one to twenty thousand hertz, with the nearest note name, its offset in cents, and the fractional MIDI number.
A note explaining that equal temperament divides the octave into twelve parts with a semitone ratio of two to the one twelfth, and that each octave doubles the frequency.

The conversion rests on equal temperament. Each semitone is a fixed ratio rather than a fixed number of hertz, so the whole scale can be generated by multiplying from a single reference; the reference here is whichever A4 you have set, and everything else is measured relative to it. That is why the tuning slider matters. Historical instruments and some ensembles tune to four hundred and fifteen or four hundred and thirty two rather than four hundred and forty, and moving the reference shifts every note proportionally rather than shifting them all by the same number of hertz. Reading the second panel in reverse is just as useful. A measured frequency is almost never exactly on a note, so the tool reports the nearest one and the offset in cents, which is the unit that matters for tuning: a hundred cents is a semitone, so a reading of twenty cents sharp describes a pitch that is a fifth of the way to the next note. The fractional MIDI number is the same information in the scale used by software, where a whole number is a note and the fraction is the detuning. Both directions are exact arithmetic, so a frequency typed in and converted to a note and back lands on the same figure.

What it does not do:

No audio input, so a frequency has to come from a meter or from your own reading.
No temperament other than equal, so a historically tempered interval will not match exactly.
Nothing about the pitch of a recording in the sense of analysis over time.
No instrument-specific transposition, so a transposing instrument's written note is not converted.
The nearest note is chosen by frequency, so a microtonal system will read as a series of detunings.
Nothing is uploaded; the arithmetic runs in the page.

Use it when a frequency has to become a note name, or a note name a frequency: checking where a filter's resonance sits, working out what a measured pitch is in cents, or setting a generator to an exact frequency. When the interval between two notes is the question rather than a single pitch, the interval calculator answers with the interval name, the ratio and the cents, and the cents calculator works entirely in the tuning-offset unit.

How to use Note Frequency Calculator

Set the tuning reference if the material is not at modern pitch.
Type a note name such as A4 or E flat 2 to read its frequency and MIDI number.
Or type a frequency to read the nearest note, its cents offset and the fractional MIDI number.
Move the reference slider to see how every note moves with the tuning.

When to use Note Frequency Calculator vs related tools

Note Frequency Calculator is the converter to reach for when a note name and a frequency have to be exchanged, in either direction and at any tuning reference. Cents Calculator works purely in tuning offsets, and MIDI Note to Frequency and Frequency to MIDI Note each do one direction of the same conversion in the scale software uses. To measure a real instrument rather than calculate, Guitar Tuner and Instrument Tuner listen instead.

Privacy & Security

This tool runs entirely in your browser — no data ever leaves your device. There is no server round-trip, no upload, no logging, and no account required. Your input is processed locally using client-side JavaScript and is never stored, transmitted, or accessible to anyone else. When you close the tab, everything disappears.