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About C♯8
C♯8 / D♭8 has a frequency of 4.435 kHz in standard tuning, where A4 is fixed at 440 Hz. It is MIDI note 109, outside the range of a standard piano.
In equal temperament every semitone multiplies the frequency by the twelfth root of two (≈1.05946), so C♯8 is 40 semitones above A4: f = 440 × 2^((109 − 69) / 12) = 4,434.92 Hz. The number in the name is the octave in scientific pitch notation, which starts each octave on C.
C♯8 and D♭8 are enharmonic: on a piano or in equal temperament they are the same key and the same frequency, but they are spelled differently depending on the key signature.
C♯8 frequency in different tunings
| Tuning reference | C♯8 frequency |
|---|---|
| A4 = 440 Hz (ISO 16 standard) | 4.435 kHz |
| A4 = 442 Hz (many European orchestras) | 4.455 kHz |
| A4 = 443 Hz (Berlin, Vienna) | 4.465 kHz |
| A4 = 435 Hz (French diapason normal, 1859) | 4.385 kHz |
| A4 = 432 Hz (alternative tuning) | 4.354 kHz |
| A4 = 415 Hz (Baroque pitch) | 4.183 kHz |
| C4 = 256 Hz (scientific pitch) | 4.34 kHz |
Intervals from C♯8
| Interval | Note | Frequency | Ratio (just) |
|---|---|---|---|
| Minor second | D8 | 4.699 kHz | 16:15 |
| Major second | D♯8 | 4.978 kHz | 9:8 |
| Minor third | E8 | 5.274 kHz | 6:5 |
| Major third | F8 | 5.588 kHz | 5:4 |
| Perfect fourth | F♯8 | 5.92 kHz | 4:3 |
| Tritone | G8 | 6.272 kHz | 45:32 |
| Perfect fifth | G♯8 | 6.645 kHz | 3:2 |
| Minor sixth | A8 | 7.04 kHz | 8:5 |
| Major sixth | A♯8 | 7.459 kHz | 5:3 |
| Minor seventh | B8 | 7.902 kHz | 9:5 |
| Major seventh | C9 | 8.372 kHz | 15:8 |
| Octave | C♯9 | 8.87 kHz | 2:1 |
Frequently asked questions
What is the frequency of C♯8?
C♯8 is 4.435 kHz when A4 = 440 Hz (4.354 kHz if A4 = 432 Hz).
What MIDI number is C♯8?
C♯8 is MIDI note number 109.
Is C♯8 on a piano?
No – a standard 88-key piano runs from A0 to C8, so C♯8 is outside its range.