Musical Note Frequency Calculator
Frequency of a note a number of semitones from A4, with its MIDI number, wavelength and the octave above.
Results
What this tool does
Count semitones up as positive and down as negative from A above middle C: C5 is three up, middle C is nine down. The reference pitch is adjustable because it is not universal — 440 Hz is the modern standard, orchestras often tune to 442 or 443, and baroque performance frequently uses 415, a full semitone lower.
Formula
f = 440 × 2^(n ÷ 12)
Variables
| Symbol | Meaning | Unit |
|---|---|---|
st | Semitones from A4 | — |
a4 | Reference pitch (A4) | Hz |
FR | Frequency | Hz |
MD | MIDI note number | — |
WL | Wavelength | m |
OC | Frequency | Hz |
FT | Frequency | Hz |
Worked example
- Semitones from A43
- Reference pitch (A4)440 Hz
- Frequency523.25113 Hz
- MIDI note number72
- Wavelength0.65552 m
- Frequency1046.5023 Hz
- Frequency554.3653 Hz
Limitations
- The default values are typical reference figures, not measurements of your situation. Replace them with your own data whenever you have it.
- The calculation runs at full precision and only the display is rounded. If you copy an intermediate value and retype it, small differences can appear.
- The formula assumes ideal conditions: no friction losses, no air resistance and no efficiency losses unless you enter them.
Frequently asked questions
Why is the twelfth root of two involved?
Because equal temperament divides the octave — a doubling of frequency — into twelve identical steps, and the only way to make twelve equal multiplications reach exactly two is for each to be the twelfth root of two, about 1.0595. The cost is that no interval except the octave is perfectly in tune: a tempered fifth is two cents flat of a true 3:2. That small, evenly spread wrongness is what lets a keyboard play in every key.