Note ↔ Frequency Calculator
Convert a musical note to Hz, or enter any frequency to find its nearest note, octave, MIDI number, and tuning difference in cents.
Choose a musical note
frequency = A4 × 2^((MIDI note − 69) ÷ 12)Note frequency chart at A4 = 440 Hz
One octave of equal-tempered note frequencies. Each octave above doubles the frequency; each octave below halves it.
| Note | Frequency | MIDI | Period |
|---|---|---|---|
| C4 | 261.63 Hz | 60 | 3.822 ms |
| C♯4 | 277.18 Hz | 61 | 3.608 ms |
| D4 | 293.66 Hz | 62 | 3.405 ms |
| D♯4 | 311.13 Hz | 63 | 3.214 ms |
| E4 | 329.63 Hz | 64 | 3.034 ms |
| F4 | 349.23 Hz | 65 | 2.863 ms |
| F♯4 | 369.99 Hz | 66 | 2.703 ms |
| G4 | 392 Hz | 67 | 2.551 ms |
| G♯4 | 415.3 Hz | 68 | 2.408 ms |
| A4 | 440 Hz | 69 | 2.273 ms |
| A♯4 | 466.16 Hz | 70 | 2.145 ms |
| B4 | 493.88 Hz | 71 | 2.025 ms |
What the cents value means
A semitone contains 100 cents. In frequency-to-note mode, +18 cents means the entered frequency is 18 cents sharp of the displayed note; a negative result means it is flat.
This is useful for identifying resonances, tuning samples and 808s, checking oscillator output, or translating an analyzer reading into a musical note. Equal temperament divides every octave into twelve equal pitch ratios.
Frequently asked questions
What frequency is A4?+
A4 is 440 Hz under the common modern tuning reference. This calculator lets you change that reference for historical, orchestral, or creative tuning systems.
What note is 440 Hz?+
At A4 = 440 Hz, a 440 Hz tone is exactly A4, MIDI note 69, with a cents offset of zero.
Why are there two names for black-key notes?+
C♯ and D♭ describe the same pitch in equal temperament but have different harmonic spellings. This calculator displays sharp names to keep the converter compact.
How accurate is frequency-to-note conversion?+
The math is precise for twelve-tone equal temperament. A real instrument can contain overtones and unstable pitch, so use a clean fundamental-frequency reading for the best identification.