C♯3 / D♭3
138.591Hz at concert pitch
Press to hear a pure sine tone at this pitch.
MIDI note
49
Piano key
29
Octave
3
Frequency
138.591 Hz
Period
7.2155 ms
Wavelength
2.4749 m
Pitch class
C♯
Notation
SPN
MIDI is the note number synths and software pass around (0–127). Pitch class is the note without its octave — all the C♯s share one. Enharmonic spellings (C♯3 and D♭3) name the same pitch two ways.
At other reference pitches
| Reference (A4) | C♯3 frequency | Where you meet it |
|---|---|---|
| 432 Hz | 136.071 Hz | the alternative-tuning circle |
| 440 Hzstandard | 138.591 Hz | the ISO 16 standard — concert pitch |
| 442 Hz | 139.221 Hz | many European orchestras tune a touch sharp |
| 443 Hz | 139.536 Hz | some sharper continental orchestras |
Every row is C♯3 — only the A4 you tune to changes. A frequency scales straight with the reference: C♯3 at 432 Hz is the 440 Hz value times 432⁄440.
Move around
Every C♯
Chords with C♯ in them
C♯ appears in each of these — see the whole chord grid.