# B Diminished piano chord (Bdim)

Bdim contains B, D and F. Two stacked minor thirds. Every note is a white key.

- Canonical page: https://piano.org/chords/diminished/b/
- Entity: chord:diminished:b
- Notes: B D F
- Formula: 1 ♭3 ♭5
- Intervals from root: P1, m3, TT
- Interval stack (semitones): 3 3
- Also written: Bdim, Bdim, B diminished
- Parameters: A440, 12-TET, 165 mm octave, spans centre to centre

## Construction

| Degree | Note | Interval from root | Semitones |
| --- | --- | --- | --- |
| 1 | B | Perfect unison | 0 |
| ♭3 | D | Minor third | 3 |
| ♭5 | F | Tritone | 6 |

## Fingering

Rest your right hand over the notes with finger 1 on B, finger 3 on D, finger 5 on F. The left hand mirrors it.
Right hand 1-3-5, left hand 5-3-1. Source: piano.org fingering method v1.

## Inversions

| Position | Bass | Notes in order | Figured bass | Span |
| --- | --- | --- | --- | --- |
| Root position | B | B3 D4 F4 | 5/3 | 6 st, 83 mm |
| First inversion (Bdim/D) | D | D4 F4 B4 | 6/3 | 9 st, 124 mm |
| Second inversion (Bdim/F) | F | F4 B4 D5 | 6/4 | 9 st, 124 mm |

## Voicings (5)

| Voicing | Notes | Span | Relation | Omits or adds |
| --- | --- | --- | --- | --- |
| Close, root position | B3 D4 F4 | 6 st, 83 mm | identical | none |
| Close, first inversion | D4 F4 B4 | 9 st, 124 mm | identical | none |
| Close, second inversion | F4 B4 D5 | 9 st, 124 mm | identical | none |
| Open, fifth on top | B2 F3 D4 | 15 st, 206 mm | identical | none |
| Root and third only | B3 D4 | 3 st, 41 mm | subset | omits F |

## Diatonic function by key

| Key | Roman numeral | Function |
| --- | --- | --- |
| C major | vii° | Dominant function |
| A minor | ii° | Predominant |

Classification system: common-practice functional harmony.

## Progressions (2)

| Progression | Key | Role | Sequence | Voice leading |
| --- | --- | --- | --- | --- |
| vii°, I | C major | vii° | Bdim to C | Bdim opens the phrase |
| ii°, v, i | A minor | ii° | Bdim to Em to Am | Bdim opens the phrase |

## One-edit neighbors

| Becomes | Edit | Changes | Common tones |
| --- | --- | --- | --- |
| Bm7♭5 | 1 ♭3 ♭5 ♭7 | adds A | 3 |
| Bdim7 | 1 ♭3 ♭5 ♭♭7 | adds A♭ | 3 |
| Bm | 1 ♭3 5 | F becomes F♯ | 2 |
| Bm7 | 1 ♭3 5 ♭7 | F becomes F♯, A | 2 |
| BmMaj7 | 1 ♭3 5 7 | F becomes F♯, A♯ | 2 |
| Bm6 | 1 ♭3 5 6 | F becomes F♯, G♯ | 2 |
| B | 1 3 5 | D, F becomes D♯, F♯ | 1 |
| Baug | 1 3 ♯5 | D, F becomes D♯, F× | 1 |
| Bsus2 | 1 2 5 | D, F becomes C♯, F♯ | 1 |
| Bsus4 | 1 4 5 | D, F becomes E, F♯ | 1 |

## Set theory

- Absolute pitch classes: {11, 2, 5}
- Relative pitch classes: [0, 3, 6]
- Normal order: [11, 2, 5]
- Prime form: (036)
- Forte number: 3-10
- Interval vector: <002001>

## Frequencies (close root position)

| Note | MIDI | Frequency |
| --- | --- | --- |
| B3 | 59 | 246.94 Hz |
| D4 | 62 | 293.66 Hz |
| F4 | 65 | 349.23 Hz |

## Questions and answers

### What notes are in Bdim?

Bdim contains B, D and F. The formula is 1, ♭3, ♭5.

### How do you play Bdim on piano?

Play B, D and F together. Right hand fingers 1, 3, 5; left hand 5, 3, 1. Every note is a white key.

### What are the inversions of Bdim?

3 positions: root position B D F, Bdim/D, Bdim/F.

### What keys contain Bdim?

2: vii° in C major, ii° in A minor.

### What is the difference between Bdim and Bm7♭5?

Adds A. 3 of the notes are shared.

### What is an easy Bdim for small hands?

The root and third only voicing, B3 D4, spans 3 semitones or about 41 mm.

### What are the frequencies of Bdim?

From B3 at A440 in 12-TET: 246.94, 293.66, 349.23 Hz.

### What is the set class of Bdim?

Prime form (036), Forte 3-10, interval vector &lt;002001&gt;.

### How do I transpose Bdim to another key?

Keep the 1, ♭3, ♭5 formula on the new root. Cdim is C, E♭, G♭; C♯dim is C♯, E, G.

### Is C♭dim the same as Bdim?

Enharmonically yes: the same piano keys and the same sound, spelled differently.

## Provenance

Every derived value above is computed by the piano.org theory kernel from the root, the quality and the stated parameters. Nothing is hand-entered per chord.

Machine record: https://piano.org/api/knowledge/v1/entities/chord:diminished:b
Last reviewed: 2026-08-12