The short version
- Bdim is B diminished. Its notes are B, D and F (formula 1 – ♭3 – ♭5).
- Easiest way to play it: a no-barre shape at the 2nd fret, frets x 2 3 4 3 x from low E to high E (x = don’t play).
- It sounds tense, spooky, unresolved. Use it as a passing chord that leads up a semitone (Bdim to C), or as the vii° of a major key.
- Bdim turns up in 2 keys: C major (as the vii°) and A minor (as the ii°).
- Try it in: C – F – Bdim – C, the diminished chord as the leading-tone chord, pulling up a semitone.
How to play Bdim on guitar, step by step
Start with the shape marked “Start here” above: the movable shape, root on the 5th string (2nd fret).
- Put your index finger on fret 2 of the 5th (A) string.
- Put your middle finger on fret 3 of the 4th (D) string.
- Put your ring finger on fret 3 of the 2nd (B) string.
- Put your little finger on fret 4 of the 3rd (G) string.
- Don’t play the low E and high E strings: skip them, or touch them lightly with a spare finger so they can’t ring.
- Strum from the 5th (A) string down, then press Strum on this page to check it sounds the same.
Once that’s comfy, try the other shape. Shape 2 is the barre chord, root on the 6th string (7th fret): 7 8 9 7 x x. Same chord, different spot on the neck, which helps when the next chord lives nearby.
Slide it around: this shape has no open strings and no barre, so the same fingering works on any fret. Move it up two frets and it becomes C♯dim. One shape, twelve chords, zero extra homework.
Notes in the Bdim chord
Bdim is built from 3 notes. On guitar you’ll often play some of them twice, on different strings. That’s normal; the chord is still Bdim.
| Note | Interval | What it does |
|---|---|---|
| B | 1 root | Names the chord and anchors the bass. |
| D | ♭3 minor third | Makes it minor (sad). |
| F | ♭5 diminished fifth | The tense, spooky bit. |
What Bdim sounds like, and when to use it
Two minor thirds stacked up. Tense and a little spooky: the chord that plays in old films when the villain twirls his moustache. Use it as a passing chord that leads up a semitone (Bdim to C), or as the vii° of a major key.
What key is Bdim in?
Bdim turns up in 2 keys: C major (as the vii°) and A minor (as the ii°). Tap a key to see the rest of its chords on the circle of fifths.
| Key | Numeral | Spelled as |
|---|---|---|
| C major | vii° | Bdim |
| A minor | ii° | Bdim |
Chords that go with Bdim
Here’s a progression to try: C – F – Bdim – C (I–IV–vii°–I), the diminished chord as the leading-tone chord, pulling up a semitone.
More progressions → Transpose it →
Using Bdim in a Suno prompt
Suno pays attention to chord names in a style prompt, at least some of the time. Put the progression in, keep the BPM, and let it fill in the rest. Then compare its guitar part with the shapes above.
Dark cabaret, 88 BPM, chord progression C – F – Bdim – C, diminished passing chords, theatrical piano, creeping strings, mysterious and playful vocals
Bdim chord FAQ
What notes are in the Bdim chord?
Bdim has 3 notes: B (the root), D (the minor third) and F (the diminished fifth). The chord formula is 1 – ♭3 – ♭5.
How do you play Bdim on guitar?
The medium way is movable shape, root on the 5th string (2nd fret). Strings from low E to high E: x 2 3 4 3 x (x means don’t play that string). Put your index finger on fret 2 of the 5th (A) string. Put your middle finger on fret 3 of the 4th (D) string. Put your ring finger on fret 3 of the 2nd (B) string. Put your little finger on fret 4 of the 3rd (G) string. Don’t play the low E and high E strings: skip them, or touch them lightly with a spare finger so they can’t ring.
What does the “dim” in Bdim mean?
It tells you the chord type: Bdim is B diminished. Two minor thirds stacked up. Tense and a little spooky: the chord that plays in old films when the villain twirls his moustache.
What key is Bdim in?
Bdim turns up in 2 keys: C major (as the vii°) and A minor (as the ii°). Major keys: C major. Minor keys: A minor.
What is the difference between Bdim and Bm?
Both have a minor third. Bm has a perfect fifth (F♯); Bdim drops it a semitone to F, which makes it tense and unstable.
What chords go well with Bdim?
Try C, G7, Dm and Am. The progression C – F – Bdim – C (I–IV–vii°–I) is the diminished chord as the leading-tone chord, pulling up a semitone. Press Play progression on this page to hear it.
Other diminished chords
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