B Diminished 7th
Hear the B Diminished 7th chord played for you.
B°7
B – D – F – G♯
Formula:R-m3-d5-d7
Intervals:P1-m3-d5-d7
Scale Degrees:1-b3-b5-bb7
Introduction
The B Diminished 7th chord is a four-note chord made up of B, D, F, and G♯. It is built from a root, minor third, diminished fifth, and diminished seventh.
The B Diminished 7th piano chord (Bdim7) consists of the notes B, D, F, G#. It is built by stacking three minor thirds, creating a fully symmetrical 4-note chord, giving it a extremely tense and dramatic character, fully symmetrical and harmonically versatile. Formula: R-m3-d5-d7 | Scale degrees: 1-b3-b5-bb7.
Notes
B Diminished 7th Inversions
| Position | Notes |
|---|---|
| Root Position | B – D – F – G# |
| 1st Inversion | D – F – G# – B |
| 2nd Inversion | F – G# – B – D |
| 3rd Inversion | B – D – F – G# |
Key Signature
The key of B Diminished 7th has 5 sharps.
F♯C♯G♯D♯A♯
Order of sharps
Sharps are added to a key signature in a fixed order. Each new sharp key adds the next sharp on the list.
F♯C♯G♯D♯A♯E♯B♯
Mnemonic: Father Charles Goes Down And Ends Battle
Chords in the Key of B Major
These are the diatonic triads built on each degree of the B major scale:
C
D
E
F
G
A
B
C
D
E
F
G
A
B
I — B Major (major)
Theory: Intervals
Formula: R-m3-d5-d7
Intervals: P1-m3-d5-d7
The B Diminished 7th is built by stacking intervals from the root note. The formula R-m3-d5-d7 describes the scale degrees used. The intervals P1-m3-d5-d7 show the distance between each note in the chord.
B Diminished 7th — Frequently Asked Questions
What notes are in the B Diminished 7th chord?
The B Diminished 7th chord (Bdim7) contains four notes: B (root), D (minor third), F (diminished fifth), and Ab (diminished seventh). All four notes are spaced exactly 3 semitones apart.
How does B Diminished 7th differ from B Diminished?
B Diminished is a three-note triad (B, D, F). B Diminished 7th adds Ab as the diminished seventh, completing the symmetrical four-note structure and maximising harmonic tension.
Why is the Diminished 7th chord symmetrical?
Bdim7 contains the same pitches as Ddim7, Fdim7, and Abdim7 — all inversions of the same four notes (B, D, F, Ab). Only three unique dim7 chords exist.
How is B Diminished 7th used in music?
Bdim7 is the vii°7 chord in C Major — the most common key in music. It resolves up by half step to C Major and appears constantly in classical cadences, jazz turnarounds, and pop as a leading-tone chord.
What songs use Diminished 7th chords?
Diminished 7th chords appear in Michelle (Beatles), throughout Chopin and Beethoven, and in jazz standards. Bdim7 is one of the most frequently encountered dim7 chords because C Major is the most common key.
How many unique Diminished 7th chords exist?
Only three. Bdim7 shares its notes with Ddim7, Fdim7, and Abdim7. The other two groups are Cdim7 and Dbdim7.
Practice Tips
- Bdim7 (B–D–F–Ab) is the vii°7 in C Major — the most important leading-tone chord in the most common key. Practice Bdim7 → C Major until it is automatic.
- Notice all four notes alternate between white and black keys — a helpful physical pattern for quick recall.
- Verify symmetry: Bdim7 and Ddim7 are the same notes. Play both to confirm.
- Use Bdim7 as a passing chord: Bm7 → Bdim7 → Am7 for smooth chromatic descent in jazz.
- Practice arpeggiating Bdim7 across multiple octaves — the repeating 3-semitone pattern creates a dramatic ascending line used in classical music.
- Bdim7 in first inversion (D–F–Ab–B) is identical to Ddim7 — use this to internalise the three-chord symmetry rule.
Related Tools
Chord FinderLook up any chord — see the notes, hear it, and play along.Chord DrillTimed drills to build speed and recognition across all chord types.Practice RoomPlug in a MIDI keyboard and get real-time feedback on every chord and scale.Circle of FifthsVisualize key relationships, relative minors, and key signatures.MIDI MonitorLive MIDI message stream with note names, velocity, and a scrolling staff.