C♯4 / D♭4
Reviewed for accuracy · Maintained by Justin Evans
C♯4 highlighted — use the view toggle to see all 88 keys.
Piano key
41 of 88
Octave
4
Frequency
277.18 Hz
MIDI number
61
Key color
Black key
Pitch class
C# · Db · B##
What is C♯4?
C♯4 is the C♯ in octave 4 — the 41st key of the 88 on a full-size piano, counted from the bottom. In standard tuning it sounds at 277.18 Hz. It sits 1 half-step above middle C (C4).
To find it, locate any group of two black keys: the white key just to their left is a C. Count up from middle C (C4) within the same octave to reach octave 4, then step to C♯.
Every octave doubles the frequency: the C♯ one octave up sounds at 554.36 Hz and the one below at 138.59 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: