B2
Reviewed for accuracy · Maintained by Justin Evans
B2 highlighted — use the view toggle to see all 88 keys.
Piano key
27 of 88
Octave
2
Frequency
123.47 Hz
MIDI number
47
Key color
White key
Pitch class
B · Cb · A##
What is B2?
B2 is the B in octave 2 — the 27th key of the 88 on a full-size piano, counted from the bottom. In standard tuning it sounds at 123.47 Hz. It sits 13 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) 2 octaves to reach octave 2, then step to B.
Every octave doubles the frequency: the B one octave up sounds at 246.94 Hz and the one below at 61.74 Hz. The same piano key can be written as B, Cb, A## depending on the musical context — same sound, different spelling.
Nearby notes
Every B on the keyboard: