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About C♯3
C♯3 / D♭3 has a frequency of 138.59 Hz in standard tuning, where A4 is fixed at 440 Hz. It is MIDI note 49 and key number 29 on an 88-key piano.
In equal temperament every semitone multiplies the frequency by the twelfth root of two (≈1.05946), so C♯3 is 20 semitones below A4: f = 440 × 2^((49 − 69) / 12) = 138.59 Hz. The number in the name is the octave in scientific pitch notation, which starts each octave on C.
C♯3 and D♭3 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♯3 frequency in different tunings
| Tuning reference | C♯3 frequency |
|---|---|
| A4 = 440 Hz (ISO 16 standard) | 138.59 Hz |
| A4 = 442 Hz (many European orchestras) | 139.22 Hz |
| A4 = 443 Hz (Berlin, Vienna) | 139.54 Hz |
| A4 = 435 Hz (French diapason normal, 1859) | 137.02 Hz |
| A4 = 432 Hz (alternative tuning) | 136.07 Hz |
| A4 = 415 Hz (Baroque pitch) | 130.72 Hz |
| C4 = 256 Hz (scientific pitch) | 135.61 Hz |
Where to play C♯3 on a guitar
Standard tuning (E A D G B E), frets 0–22.
- 6th string (low E), fret 9
- 5th string (A), fret 4
Intervals from C♯3
| Interval | Note | Frequency | Ratio (just) |
|---|---|---|---|
| Minor second | D3 | 146.83 Hz | 16:15 |
| Major second | D♯3 | 155.56 Hz | 9:8 |
| Minor third | E3 | 164.81 Hz | 6:5 |
| Major third | F3 | 174.61 Hz | 5:4 |
| Perfect fourth | F♯3 | 185 Hz | 4:3 |
| Tritone | G3 | 196 Hz | 45:32 |
| Perfect fifth | G♯3 | 207.65 Hz | 3:2 |
| Minor sixth | A3 | 220 Hz | 8:5 |
| Major sixth | A♯3 | 233.08 Hz | 5:3 |
| Minor seventh | B3 | 246.94 Hz | 9:5 |
| Major seventh | C4 | 261.63 Hz | 15:8 |
| Octave | C♯4 | 277.18 Hz | 2:1 |
Instruments and voices that can play C♯3
Frequently asked questions
What is the frequency of C♯3?
C♯3 is 138.59 Hz when A4 = 440 Hz (136.07 Hz if A4 = 432 Hz).
What MIDI number is C♯3?
C♯3 is MIDI note number 49.
Is C♯3 on a piano?
Yes – it is key 29 of 88.
Where is C♯3 on the guitar?
In standard tuning: 6th string (low E), fret 9; 5th string (A), fret 4.