C♯3 / D♭3
Reviewed for accuracy · Maintained by Justin Evans
C♯3 highlighted — use the view toggle to see all 88 keys.
Piano key
29 of 88
Octave
3
Frequency
138.59 Hz
MIDI number
49
Key color
Black key
Pitch class
C# · Db · B##
What is C♯3?
C♯3 is the C♯ in octave 3 — the 29th key of the 88 on a full-size piano, counted from the bottom. In standard tuning it sounds at 138.59 Hz. It sits 11 half-steps below middle C (C4).
To find it, locate any group of two black keys: the white key just to their left is a C. Count down from middle C (C4) 1 octave to reach octave 3, then step to C♯.
Every octave doubles the frequency: the C♯ one octave up sounds at 277.18 Hz and the one below at 69.3 Hz. The same piano key can be written as C#, Db, B## depending on the musical context — same sound, different spelling.
Nearby notes
Every C♯ on the keyboard: