Note Name, MIDI Number and Frequency (Hz) Converter
Enter any one of a note name, a MIDI note number or a frequency in hertz and the other two are calculated in 12-tone equal temperament. The A4 reference pitch is 440 Hz by default and can be changed to 442 Hz, 432 Hz and so on. Start from a frequency to also see the nearest note and how many cents off it is. To check a pitch with your microphone, try the Instrument Tuner. Everything is calculated on this page and nothing is sent anywhere.
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C4 is middle C. Octaves run from -1 to 9, and #, b, ♯ and ♭ are accepted.
Result
Note frequency table
Frequencies in Hz from C0 to B8 at the current reference pitch. Click a value to copy it.
| Octave | C | C# | D | D# | E | F | F# | G | G# | A | A# | B |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 0 | ||||||||||||
| 1 | ||||||||||||
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| 8 |
How to use
- If needed, change "Reference pitch A4 (Hz)". It is usually 440 Hz, and orchestras often use 442 Hz.
- Type into any one of "Note name (e.g. C#4, Bb3)", "MIDI note number (0-127)" or "Frequency (Hz)". The other fields update automatically.
- Check the nearest note and its offset in cents under "Result".
- For frequencies across the whole range, click a value in "Note frequency table" to copy it.
Notes
- Values use 12-tone equal temperament, which splits the octave into 12 equal steps. Other tunings, such as just intonation, give different frequencies.
- Octave numbers follow scientific pitch notation (C4 = middle C = MIDI 60). Some software calls middle C C3, so octaves can look shifted by one.
- Frequencies are shown to two decimal places. The calculation itself is not rounded.
- Note names are accepted for MIDI 0 to 127 (C-1 to G9), and frequencies from 1 to 30000 Hz.
- When you start from a frequency, the note name field shows the nearest note and the MIDI field shows the fractional value. The offset from that note is shown in cents under "Result".
Glossary
Equal temperament
A tuning that divides the octave (a doubling of frequency) into 12 equal semitones, each a ratio of the 12th root of 2, about 1.0595. Every key sounds the same, and it is the standard for pianos and electronic instruments.
Cent
A unit for pitch differences: a semitone is 100 cents and an octave is 1200 cents. Most listeners cannot hear an offset of about 5 cents.
Reference pitch (A4)
The frequency of the A above middle C that all tuning is based on. The international standard is 440 Hz, orchestras often use around 442 Hz, and Baroque music around 415 Hz.
MIDI note number
An integer from 0 to 127 that names a pitch. Middle C (C4) is 60 and A4 is 69, and each step up is one semitone.
Scientific pitch notation
A way of writing a note with an octave number, such as C4 or A#3. C4 is middle C, and the octave number changes at each C.
FAQ
What is the frequency of middle C (C4) when A4 is 440 Hz?
About 261.63 Hz. C4 is nine semitones below A4, so it is 440 × 2^(-9/12). With A4 set to 442 Hz it becomes about 262.82 Hz.
What is the formula to get a MIDI note number from a frequency?
MIDI note = 69 + 12 × log2(frequency / reference pitch). 440 Hz gives 69 and 880 Hz gives 81. When the result is not a whole number, the fractional part is the pitch offset, and multiplying it by 100 gives cents.
Why does some software call middle C "C3"?
Programs number octaves differently. This tool uses scientific pitch notation, where C4 is middle C (MIDI 60). Some DAWs and Yamaha-style notation call middle C "C3", so the octave looks shifted by one.
What changes if I set the reference pitch to 432 Hz or 442 Hz?
Every note scales by the same ratio. At A4 = 442 Hz, all notes are about 7.85 cents higher than at 440 Hz. The intervals between notes stay the same.
How different are equal temperament and just intonation?
A major third is about 1.2599 times the root in equal temperament but exactly 1.25 times in just intonation, a gap of about 14 cents. This tool only covers equal temperament.
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