Examples
Examples
Try the starting example
- Measured frequency (Hz)
- 440
- Reference A4 frequency (Hz)
- 440
- Enharmonic spelling: sharps or flats
- sharps
- Nearest equal-tempered note
- A4
- Nearest MIDI note number
- 69
- Ideal note frequency (Hz)
- 440
- Cents above or below nearest note
- 0
Try another scenario
- Measured frequency (Hz)
- 880
- Reference A4 frequency (Hz)
- 442
- Enharmonic spelling: sharps or flats
- flats
- Nearest equal-tempered note
- A5
- Nearest MIDI note number
- 81
- Ideal note frequency (Hz)
- 884
- Cents above or below nearest note
- -7.851415
Calculation method
Calculation method
Nearest equal-tempered note
Find MIDI position 69 + 12 × (log2(frequency) − log2(reference A4)), round to nearest integer, then map to scientific note notation.
Nearest MIDI note number
Nearest integer MIDI position; exact half-semitone ties select the higher note.
Ideal note frequency (Hz)
Reference A4 × 2^((MIDI number − 69)/12).
Cents above or below nearest note
100 × (unrounded MIDI position − nearest MIDI number). Positive means sharp.
Symbols and units
- a
- Measured frequency (Hz)
- b
- Reference A4 frequency (Hz)
- c
- Enharmonic spelling: sharps or flats
Use the units shown. A list keeps the order in which you enter its values. The symbol ^ means “raised to the power of”.
Assumptions & limits
Assumptions & limits
- Twelve-tone equal temperament with C4=MIDI 60 and A4=MIDI 69. This converts a measured frequency; it does not detect pitch from microphone audio. Spelling is chromatic, not key-aware.
Are these inputs private?
These calculations run in your browser. A shared link contains the values you choose to share. Only questions submitted to the separate AI finder are sent to OpenAI.
Further reading
MIDI Association: tuning specification ↗
Background reading; this does not imply endorsement or independent review of SumFizz.