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Learn › B Diminished Chord on Piano (Bdim)

New Released in April 2026

B Diminished Chord on Piano (Bdim)

To play Bdim on the piano, press B, D, F together. Start from Bm and move the fifth down a semitone: that one key turns it into Bdim. Below: the keyboard, the three positions, how it compares with B and Bm, and where it goes next.

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Bdim B D F

Where Bdim goes

  • Bdim is the vii° chord of C major and the ii° chord of A minor.
  • It wants to move up a semitone: Bdim → C / Cm, the bottom note rising to the new root.
  • Add A and you get Bm7b5 (half-diminished); add Ab instead and you get Bdim7 (diminished 7th).

Bm7b5 · C

How to play Bdim on the piano

Move the lowest note up an octave to reach the next position.

Bdim B D F

Root position: B D F

Bdim D F B

1st inversion: D F B

Bdim F B D

2nd inversion: F B D

  • Root position: starts on B, a white key; all white keys
  • 1st inversion: starts on D, a white key; all white keys
  • 2nd inversion: starts on F, a white key; all white keys

What makes Bdim different

Same root, same third or fifth moved by a semitone.

ChordNotesThirdFifth
B B D# F#major 3rdperfect 5th
Bm B D F#minor 3rdperfect 5th
Bdim B D Fminor 3rddiminished 5th
Baug B D# F##major 3rdaugmented 5th
ChordRunner showing a chord block while hands play the piano

Train Bdim in a game

ChordRunner mixes Bdim with the chords around it and checks every note you play. MIDI keyboard or microphone, both work.

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All piano chords · Diminished chords explained

Common questions

How do you play Bdim on the piano?

Press B, D, F together: right hand 1-3-5 with the thumb on B, left hand 5-3-1 with the little finger on B.

What is the difference between Bdim and Bm?

One note. Bm has F# on top; Bdim moves it to F. The new fifth is what gives Bdim its tense sound.

Where does Bdim go?

Bdim is the vii° chord of C major and the ii° chord of A minor. It wants to move up a semitone: Bdim → C / Cm, the bottom note rising to the new root.

Can I practise Bdim with a MIDI keyboard or microphone?

Yes. ChordRunner detects a USB MIDI keyboard automatically and also hears an acoustic piano through the microphone. Bdim counts in any position, as long as B, D, F sound together.

Your instrument is the controller.

ChordRunner is a browser game that teaches piano and guitar chords: a chord appears on screen, you play it on a real instrument, and your runner jumps. MIDI keyboard or microphone, both work.

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