32.7Hz
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32.7 HzFrequency at A4 = 440 Hz
24MIDI note number
4Piano key (of 88)
10.49 mWavelength in air
About C1
C1 has a frequency of 32.7 Hz in standard tuning, where A4 is fixed at 440 Hz. It is MIDI note 24 and key number 4 on an 88-key piano.
C1 is the lowest C on a standard piano – a deep rumble at the bottom of the bass register.
In equal temperament every semitone multiplies the frequency by the twelfth root of two (≈1.05946), so C1 is 45 semitones below A4: f = 440 × 2^((24 − 69) / 12) = 32.70 Hz. The number in the name is the octave in scientific pitch notation, which starts each octave on C.
C1 frequency in different tunings
| Tuning reference | C1 frequency |
|---|---|
| A4 = 440 Hz (ISO 16 standard) | 32.7 Hz |
| A4 = 442 Hz (many European orchestras) | 32.85 Hz |
| A4 = 443 Hz (Berlin, Vienna) | 32.93 Hz |
| A4 = 435 Hz (French diapason normal, 1859) | 32.33 Hz |
| A4 = 432 Hz (alternative tuning) | 32.11 Hz |
| A4 = 415 Hz (Baroque pitch) | 30.85 Hz |
| C4 = 256 Hz (scientific pitch) | 32 Hz |
Intervals from C1
| Interval | Note | Frequency | Ratio (just) |
|---|---|---|---|
| Minor second | C♯1 | 34.65 Hz | 16:15 |
| Major second | D1 | 36.71 Hz | 9:8 |
| Minor third | D♯1 | 38.89 Hz | 6:5 |
| Major third | E1 | 41.2 Hz | 5:4 |
| Perfect fourth | F1 | 43.65 Hz | 4:3 |
| Tritone | F♯1 | 46.25 Hz | 45:32 |
| Perfect fifth | G1 | 49 Hz | 3:2 |
| Minor sixth | G♯1 | 51.91 Hz | 8:5 |
| Major sixth | A1 | 55 Hz | 5:3 |
| Minor seventh | A♯1 | 58.27 Hz | 9:5 |
| Major seventh | B1 | 61.74 Hz | 15:8 |
| Octave | C2 | 65.41 Hz | 2:1 |
Instruments and voices that can play C1
Frequently asked questions
What is the frequency of C1?
C1 is 32.7 Hz when A4 = 440 Hz (32.11 Hz if A4 = 432 Hz).
What MIDI number is C1?
C1 is MIDI note number 24.
Is C1 on a piano?
Yes – it is key 4 of 88.