How to use the enharmonic note converter
- Type a note into the box: C#4, Db, B##3 or Fb. If you leave out the octave, octave 4 is used.
- Or choose an octave and tap a key in the key grid.
- Read the list of all spellings, the MIDI number and the frequency.
- Switch the tuning reference between A4 = 440 Hz and 442 Hz.
- Check the treble and bass staves, the keyboard, and the table of key signatures.
Lowercase works too (c#4), and the unicode sharp and flat signs are accepted. Double sharps can be typed as ## or x.
What enharmonic means
Two notes are enharmonic when they sound the same pitch but have different names. On a piano each black key has two names: C sharp or D flat, D sharp or E flat, and so on. White keys have alternate names too: B sharp is C, C flat is B, E sharp is F, and F flat is E. Double accidentals add more: C double sharp sounds as D, and D double flat sounds as C.
| Pitch | Enharmonic spellings | MIDI number |
|---|---|---|
| C4 | B sharp 3, D double flat 4 | 60 |
| B3 | C flat 4, A double sharp 3 | 59 |
| C sharp 4 | D flat 4, B double sharp 3 | 61 |
| E4 | F flat 4, D double sharp 4 | 64 |
| F sharp 4 | G flat 4, E double sharp 4 | 66 |
Which spelling is correct
The correct spelling depends on the key and on the letter names around the note. In D major the note is F sharp, because the scale needs one F. In A flat major the scale uses A flat, B flat, C, D flat, E flat, F and G, so the black key between F and G is never spelled with a sharp unless the harmony asks for it. Sharp keys spell their chromatic notes with sharps, flat keys with flats. The table in the tool shows what each of the 15 major key signatures does with your note.
Common questions
Is B sharp really the same as C?
In equal temperament, yes. B sharp 3 and C4 share MIDI note 60 and the same frequency, about 261.63 Hz at A4 = 440. The spelling B sharp appears when a key or chord needs a B, for example in C sharp major, where the seventh degree is B sharp.
Why do I need double sharps and double flats?
They keep each scale degree on its own letter. In G sharp harmonic minor the seventh degree is F double sharp. Writing G instead would repeat the letter G in the scale and make the key harder to read.
What is the difference between 440 and 442 Hz?
It is the reference pitch for A4. Many orchestras tune to 440 Hz, while some tune to 442 Hz or higher for a brighter sound. Every frequency scales by the same ratio, so C4 is 261.63 Hz at 440 and 262.81 Hz at 442. The play button always uses 440.
What is a MIDI number?
MIDI numbers count semitones, with middle C as 60 and A4 as 69. Because they count sounds, enharmonic notes share one MIDI number. The spelling is separate information.
Sources
- Open Music Theory: Pitch and pitch class — Octave equivalence and pitch classes.
- Enharmonic, reference article — Enharmonic equivalents and double accidentals.
- Scientific pitch notation, reference article — Octave numbering, middle C as C4.
- Piano key frequencies, reference article — Frequency formula and MIDI note numbers.
- Concert pitch, reference article — A4 at 440 Hz and higher tuning standards.