B diminished chord (Bdim)
Bdim is B, D and F: 1–♭3–♭5 built on B. See and hear it on all three instruments below.
On guitar
x-2-3-4-3-x · movable · medium
- Notes
- B · D · F
- Formula
- 1 · ♭3 · ♭5
- First shape
- x-2-3-4-3-x
Bdim on guitar: every shape, finger by finger
On piano
root position · B–D–F · right hand 1-3-5
- Notes
- B · D · F
- Formula
- 1 · ♭3 · ♭5
Bdim on piano: fingering and inversions
On ukulele
4-2-1-2 · movable · medium
- Notes
- B · D · F
- Formula
- 1 · ♭3 · ♭5
- First shape
- 4-2-1-2
Where Bdim usually goes next
Three changes cover most of what Bdim does in songs.
- Bdim → C (leads up a half step)
Guitar: Bdim (x-2-3-4-3-x) to C (x-3-2-0-1-0): the index finger goes to the B string, 1st fret, move the middle finger to the D string, 2nd fret, your ring finger lands on the A string, 3rd fret. Everything moves: lift the whole hand and place the new shape in one go.
Piano: Bdim to C: play C in root position (C–E–G), while B moves up to C, D up to E and F up to G. C - Bdim → Cm (leads up a half step)
Guitar: Bdim (x-2-3-4-3-x) to Cm (x-3-1-0-1-3): your index finger lands on the D string, 1st fret, the middle finger goes to the B string, 1st fret, move the ring finger to the A string, 3rd fret. Nothing carries over, so drill it slowly, lifting and landing all fingers at once.
Piano: Bdim to Cm: play Cm in root position (C–E♭–G), while B moves up to C, D up to E♭ and F up to G. Cm - Bdim → Em (iii in C major)
Guitar: Bdim (x-2-3-4-3-x) to Em (0-2-2-0-0-0): your index finger stays put, move the middle finger to the D string, 2nd fret. That makes it one of the quickest changes from this chord. The two chords share B, which is why the change sounds smooth.
Piano: Bdim to Em: play Em in 2nd inversion (B–E–G) and B stays under the same finger, while D moves up to E and F up to G. Em
How Bdim is built
Bdim is a diminished triad: two minor thirds stacked. It sounds tense and unstable and rarely stays long. Its most common job is to lead up a half step, so Bdim usually moves to C or Cm.
From B, go 3 half steps up to D then 3 half steps up to F.
| Note | Role | Half steps | Hear it |
|---|---|---|---|
| B | root | 0 | |
| D | minor third | 3 | |
| F | diminished fifth | 6 |
Keys and progressions with Bdim
Bdim belongs to 2 keys: vii° in C major and ii° in A minor.
Chords close to Bdim
- Bdim and Bm differ by one note: F in Bdim, F♯ in Bm. They share B and D. Bm
Chords that share most of their notes with Bdim: Dm6, Ddim7, Fdim7, G7, G♯dim7, Bdim7.
Every B chord
B diminished chord: questions
What notes are in the B diminished chord?
B, D and F. Bdim is built 1–♭3–♭5 from B: D is the minor third and F is the diminished fifth.
How do you play Bdim on guitar?
The usual shape is x-2-3-4-3-x (movable). All 4 guitar shapes.
How do you play Bdim on piano?
Play B, D and F with right-hand fingers 1-3-5. B sits just right of the group of three black keys. Inversions and left hand.
How do you play Bdim on ukulele?
4-2-1-2 in standard GCEA tuning. More ukulele shapes.
What key is Bdim in?
Bdim belongs to 2 keys: vii° in C major and ii° in A minor.
What's the difference between Bdim and Bm?
Bdim and Bm differ by one note: F in Bdim, F♯ in Bm. They share B and D.
All three instruments are drawn and played from B, D and F by the same engine. Updated September 2026.