Type a note such as C4, F#3 or Bb5, or tap a key on the piano, and this free note to frequency converter shows its exact frequency in hertz. Switch the tuning between A4 = 440, 432, 442 and 415 Hz or enter your own, fine-tune in cents, hear the note, and see the notes of its octave and the same note in every octave.
Note to Frequency Converter
Type a note like C4, F#3, Bb5 or “middle C”, or pick below.
A4 =
440.00Hz
with A4 = 440 Hz
- MIDI note
- 69
- Piano key
- 49 of 88
- Period
- 2.273 ms
- Wavelength in air
- 78.0 cm
- Same note at A4 = 432 Hz
- 432.00 Hz (−31.8 cents)
| Note | Frequency |
|---|---|
| 261.63 Hz | |
| 277.18 Hz | |
| 293.66 Hz | |
| 311.13 Hz | |
| 329.63 Hz | |
| 349.23 Hz | |
| 369.99 Hz | |
| 392.00 Hz | |
| 415.30 Hz | |
| 440.00 Hz | |
| 466.16 Hz | |
| 493.88 Hz |
| Note | Frequency |
|---|---|
| 27.50 Hz | |
| 55.00 Hz | |
| 110.00 Hz | |
| 220.00 Hz | |
| 440.00 Hz | |
| 880.00 Hz | |
| 1760.00 Hz | |
| 3520.00 Hz | |
| 7040.00 Hz |
Related Tools
- Frequency to Note Converter
The other direction: type Hz, get the note and cents.
- Chromatic Tuner
Tune any instrument to the frequencies shown here.
- Pitch Shifter
Change the pitch of a song or recording.
- Pitch Detector
See the note you sing or play in real time.
How to Convert a Note to Hz
- Type the note name and octave in the box: a letter A–G, an optional sharp (# or ♯) or flat (b or ♭) and the octave number. “Middle C” works too.
- Or tap a note button and set the octave with − and +, or tap a key on the 88-key piano (it plays the note as well).
- Read the frequency in the answer box. Press Play to hear it and Copy to copy the result.
- Pick the A4 reference your music uses, and add a cents offset if you need a note slightly sharp or flat.
- Click any row of the octave tables to jump to that note.
Quick answer (A4 = 440 Hz): A4 = 440 Hz, middle C (C4) = 261.63 Hz, E4 = 329.63 Hz, G4 = 392.00 Hz, C5 = 523.25 Hz, and A in every octave is 27.5, 55, 110, 220, 440, 880 and 1,760 Hz.
The Note to Frequency Formula
In equal temperament each semitone multiplies the frequency by the twelfth root of two (about 1.0595), so twelve semitones make an octave, which doubles the frequency. Counting semitones from A4:
frequency = 440 × 2(n − 69) / 12, where n is the MIDI note number (C4 = 60, A4 = 69)
Example: C4 is 9 semitones below A4, so 440 × 2−9/12 = 261.63 Hz. To use another tuning, replace 440 with your A4. A worked guide with more examples is in how to convert musical notes to frequency (Hz).
Note Names, Sharps, Flats and Octaves
- Octave numbers start at C: B3 is followed by C4. Middle C is C4, and the piano runs from A0 to C8.
- Sharps and flats of the same key have the same frequency in equal temperament: C♯4 and D♭4 are both 277.18 Hz. The converter keeps the spelling you type.
- Unusual spellings such as C♭4 (= B3) and E♯4 (= F4) are converted to the key they sound on.
- MIDI numbers are shown for every note, from 0 (C−1) to 127 (G9), so you can match notes in music software.
The frequency of every note from C0 to B8 on one page is in the musical note frequency chart.
Same Note at 440 Hz and 432 Hz
Changing the reference moves every note by the same number of cents. Going from 440 to 432 Hz lowers everything by 31.77 cents, and 442 Hz raises everything by 7.85 cents. The answer box always shows the same note at the other common tuning for comparison.
| Note | A4 = 440 Hz | A4 = 432 Hz | A4 = 442 Hz | A4 = 415 Hz |
|---|---|---|---|---|
| C4 (middle C) | 261.63 | 256.87 | 262.81 | 246.76 |
| E4 | 329.63 | 323.63 | 331.13 | 310.90 |
| G4 | 392.00 | 384.87 | 393.78 | 369.72 |
| A4 | 440.00 | 432.00 | 442.00 | 415.00 |
| C5 | 523.25 | 513.74 | 525.63 | 493.52 |
Why 440 Hz became the standard, and which pitches were used before it, is covered in the A440 tuning standard and historical pitch standards. To hear a whole song at 432 Hz, lower it by 31.77 cents with the pitch shifter.
What You Can Use Note Frequencies For
- Tuning: check the target frequency of each string or pipe before you tune. Instrument tunings are listed in the instrument tuning guide.
- Sound design and synths: set oscillators, filters and resonances to musical notes.
- Mixing: find the fundamental of a bass note or kick drum to set EQ cuts and boosts.
- Physics and acoustics: the period and wavelength help with tubes, strings and room modes.
- Singing and ear training: play a note to find your starting pitch; typical note ranges are in frequency ranges for instruments and voices.
Frequently Asked Questions
What is the frequency of middle C?
Middle C (C4) is 261.63 Hz with A4 = 440 Hz, and 256.87 Hz with A4 = 432 Hz.
What is A in Hz?
A4 is 440 Hz. Every octave doubles it: A2 = 110 Hz, A3 = 220 Hz, A5 = 880 Hz. Select A to see all of them in the “in every octave” table.
What is C in Hz?
C0 = 16.35, C1 = 32.70, C2 = 65.41, C3 = 130.81, C4 = 261.63, C5 = 523.25, C6 = 1,046.50, C7 = 2,093.00 and C8 = 4,186.01 Hz.
Are these frequencies right for a piano?
They are the theoretical equal-temperament values. Real pianos are stretch-tuned, so the lowest notes are slightly flatter and the highest slightly sharper than these numbers.