THE NUMBERS, EXPLAINED
How to use this calculator.
12-tone equal temperament only; reference_hz is the frequency of MIDI note 69 (A4). Valid MIDI range is 0-127.
Start with your inputs
Enter midi note number (0-127), reference frequency for midi 69 (hz). Keep amounts in the units shown on each field. The example is a starting point, not a recommended value.
| Input | Example value |
|---|---|
| MIDI note number (0-127) | 69 |
| Reference frequency for MIDI 69 (Hz) | 440 |
A worked example
With the example inputs above, frequency (hz) is 440. Change the inputs to explore your own scenario.
| Result | Example answer |
|---|---|
| Frequency (Hz) | 440 |
| Ratio to reference A4 | 1 |
How this is calculated
Frequency (Hz)
frequency_hz (Hz): reference_hz multiplied by 2^((midi-69)/12), i.e. one equal-tempered semitone step is a factor of 2^(1/12).
Ratio to reference A4
ratio_to_a4 (dimensionless): 2^((midi-69)/12), the frequency ratio relative to the reference note MIDI 69.
Symbols and units
- midi
- MIDI note number (0-127)
- reference_hz
- Reference frequency for MIDI 69 (Hz)
Use the units shown. A list keeps the order in which you enter its values. The symbol ^ means “raised to the power of”.
Assumptions and limits
12-tone equal temperament only; reference_hz is the frequency of MIDI note 69 (A4). Valid MIDI range is 0-127.
Calculations use the values you enter. Blank or invalid inputs show an error instead of silently substituting zero. Results are displayed to useful precision; calculations retain the underlying numeric precision.
Questions about this tool
What does the result tell me?
Frequency (Hz); Ratio to reference A4. The result applies to the method and inputs described above. Check the units and assumptions before using it in a decision.
Why might another calculator differ?
Differences in units, rounding, timing or model definitions can produce different answers. Compare the input definitions and the method, rather than only the final number. For this tool: 12-tone equal temperament only; reference_hz is the frequency of MIDI note 69 (A4). Valid MIDI range is 0-127.
Are my inputs stored or sent to AI?
Calculations on this page happen in your browser. The separate AI question finder sends its submitted conversation to OpenAI; these calculator fields are not sent. Favourites and recent tool names are stored locally. A shared link contains the inputs you choose to include.
Further reading
UNSW Music Acoustics: note names, MIDI numbers and frequencies ↗
Background reading; this does not imply endorsement or independent review of SumFizz.
Review status
Software example and browser checks are recorded in our quality report. No external expert review is claimed. Created with coding assistance; calculations run as ordinary browser code.
Read the quality report →