Musical Note Frequency Generator
Convert between musical note names (A4, C#3, Bb2...) and their frequency in Hz, using 12-tone equal temperament. Get the MIDI note number, wavelength in air, cents deviation for off-pitch frequencies, and a full reference table for the surrounding octave. Supports any A4 tuning reference (440 Hz standard, 432, 415 Baroque, 444, or custom).
Input
Standard concert pitch is 440 Hz. Try 432 (Verdi / New Age), 415 (Baroque) or 444 (modern orchestras), or enter any custom value.
Letter A-G, optional # or b for sharp/flat, then the octave number (can be negative).
Output
How far the input frequency is from the nearest equal-tempered note (0 in Note mode).
| Note | Frequency | MIDI | Wavelength |
|---|---|---|---|
| No data yet | |||
Guides
The Musical Note Frequency Generator converts between a musical note name — like A4, C#3 or Bb2 — and its frequency in Hertz, using standard 12-tone equal temperament (12-TET). Enter a note to get its frequency, or enter a frequency to find the nearest note and how far off-pitch it is in cents. Everything runs in your browser; nothing you enter is uploaded.
How it works
Every note maps to a MIDI note number, with A4 (440 Hz) fixed at MIDI 69. From there:
- Note → Frequency:
Hz = referenceHz × 2^((midi − 69) / 12) - Frequency → Note:
midi = 69 + 12 × log₂(Hz ÷ referenceHz), rounded to the nearest whole note
The reference frequency is A4's tuning — 440 Hz is standard concert pitch, but you can switch to 432 Hz (sometimes called "Verdi tuning"), 415 Hz (Baroque pitch), 444 Hz (used by some modern orchestras), or type in any custom value. Changing the reference shifts every note's frequency without changing which note a given pitch is closest to.
Reading the results
- Note — the note name and octave nearest the input (or the note you typed, echoed back).
- Frequency — the note's frequency at the chosen tuning reference, in Hz.
- MIDI Note — the standard MIDI note number (0-127; A4 = 69).
- Wavelength — the sound wave's length in air at 20°C (speed of sound 343 m/s), useful for room/speaker placement and acoustic calculations.
- Cents Offset — in Frequency → Note mode, how far the input frequency deviates from the nearest equal-tempered note, in cents (100 cents = 1 semitone). Always 0 in Note → Frequency mode, since the note is exact by definition.
- Octave Reference — all 12 notes in the surrounding octave, with their frequency, MIDI number and wavelength at the same tuning reference, so you can see the result in context.
Why isn't middle C 261.63 Hz exactly?
It is, at standard 440 Hz tuning — that's the equal-tempered value for C4, rounded to two decimal places. Switch the reference to 432 Hz and C4 shifts down to about 256.87 Hz; the note names never change, only their frequencies, because the whole 12-TET grid slides with the A4 reference.
What does a cents offset mean in practice?
Human pitch perception starts noticing a difference around 5-10 cents, and most tuners flag anything beyond ±10 cents as "out of tune." A cents offset near ±50 means the frequency sits almost exactly between two notes.
To convert between intervals (semitones, cents, frequency ratios) rather than absolute pitches, see the Musical Interval Converter.