Bdim chord on guitar
The Bdim chord, or B diminished, stacks 3 notes on B: B, D and F. Musicians write its formula 1 ♭3 ♭5.
Notes and intervals of Bdim
Each note of Bdim has a job. Counted from the root, you get root (B), minor 3rd (D) and diminished 5th (F). Change one of these intervals and you get a different chord, which is why the formula 1 ♭3 ♭5 is worth memorising rather than the shape alone.
| Degree | Interval | Note |
|---|---|---|
| 1 | root | B |
| ♭3 | minor 3rd | D |
| ♭5 | diminished 5th | F |
How to play Bdim on guitar
Start with the first diagram: x 2 0 x 0 1, read from the 6th string (low E) to the 1st string (high E). Your lowest note is B. The next positions give the same notes in a different order, which is useful when you want Bdim to sit closer to the surrounding chords.
Let the open strings ring: strum slowly once and check that every note sounds clean before you speed up.
Which keys use Bdim?
You find Bdim as a diatonic chord in C major (vii°). The most common case is C major, where it plays the role of vii°.
Scales to play over Bdim
These scales share every note of Bdim: B blues scale and B Locrian mode. B blues scale is the safest choice; the others add more colour.
About diminished chords
Two stacked minor thirds: 1 ♭3 ♭5. The diminished fifth (a tritone) makes the diminished chord the most unstable triad: tense, dark and restless. It rarely stands alone and pulls towards the chord a semitone above its root. For example Bdim: B D F. Add a diminished seventh and you get the symmetrical diminished seventh chord.
In a major key it sits on vii° (for example Bdim in C major), acting as a lighter V7 that resolves to I. In a minor key it sits on ii°. Passing diminished chords connect neighbouring chords chromatically, for example I ♯i° ii (C C♯dim Dm). Classical music, jazz, ragtime and film scores use it to build suspense.
The triad is usually played as a small three or four-string shape on the middle or top strings, since full barres are awkward. Many guitarists play dim7 instead: a movable four-string shape that repeats every 3 frets, because the chord divides the octave into equal minor thirds. Slide it up three frets to hear a new inversion.
dim (three notes) and dim7 (four notes, with a diminished seventh) are not the same, though 'dim' on a jazz chart often means dim7. And dim is not m7♭5: the half-diminished chord adds a minor seventh (for example Bm7♭5: B D F A) and sounds much softer. Symbols: ° means diminished, ø means half-diminished.
Frequently asked questions
What notes are in the Bdim chord?
Bdim (B diminished) contains B, D and F. In intervals: root (B), minor 3rd (D) and diminished 5th (F).
How do you play Bdim on guitar?
The easiest shape is x 2 0 x 0 1, from the low E string to the high E string. This page shows 3 positions with finger numbers.
What scale goes with Bdim?
B blues scale fits Bdim best. Other scales that contain all its notes: B Locrian mode.
What key is Bdim in?
Bdim belongs to C major (vii°). In C major it is the vii° chord.
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