What notes are in a B diminished chord?

B diminished contains three notes: B (the root), D (the minor third), and F (the diminished fifth).

What key uses B diminished?

B° is the vii° of C major and the ii° of A minor. Both keys have no sharps or flats; B° also uses no accidentals (all naturals).

How is B diminished different from B minor?

Only the fifth changes. B minor is B–D–F♯; B° is B–D–F. The half-step difference in the fifth turns a stable minor chord into an unstable diminished one.

Where does B diminished appear in famous music?

Constantly throughout C-major literature — Bach's C major Prelude WTC I, Mozart's C major Sonata K. 545, Beethoven's 5th Symphony finale (in C major). It's the most-played diminished triad in Western music.

B diminished chord — notes, intervals, and practice

B diminished — B, D, F — is the vii° of C major and the ii° of A minor. As the diminished triad of the most common key in Western music, B° is by far the most-played diminished chord in the literature. All three notes are naturals, making it visually the cleanest dim triad of all twelve.

Intervals

The B diminished chord stacks two thirds on the root. Each interval and its size in semitones:

B→Dminor 3rd3 semitones
D→Fminor 3rd3 semitones
B→Fdiminished 5th6 semitones

On the keyboard

Each note of the B diminished chord highlighted on a piano. Pitch class is what matters — any octave works.

On the guitar

One voicing of the B diminished chord on a six-string guitar fretboard.

Common mistakes

B° is all naturals (B–D–F) — no sharps, no flats. The most common error is misreading it as B minor (B–D–F♯) by accidentally adding the sharp. The plain-natural fifth (F) is what creates the diminished tritone B–F. On guitar, B° is rarely played as a full chord shape; it's usually a partial three-note voicing on the upper strings.

In context

B° → C major (vii° → I) is the textbook leading-tone cadence in C major. B° → E7 → A minor (ii° → V → i) is the textbook minor-key cadence. Bach's C major preludes use B° at almost every cadence; Beethoven, Mozart, and Haydn all rely on it as a primary cadential preparation in their C-major literature.

Drill it

The B diminished chord is one of 48 in the Chord Trainer. Open the full trainer to practice it alongside related chords with timing and best-time tracking.

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Frequently asked

What notes are in a B diminished chord?: B diminished contains three notes: B (the root), D (the minor third), and F (the diminished fifth).
What key uses B diminished?: B° is the vii° of C major and the ii° of A minor. Both keys have no sharps or flats; B° also uses no accidentals (all naturals).
How is B diminished different from B minor?: Only the fifth changes. B minor is B–D–F♯; B° is B–D–F. The half-step difference in the fifth turns a stable minor chord into an unstable diminished one.
Where does B diminished appear in famous music?: Constantly throughout C-major literature — Bach's C major Prelude WTC I, Mozart's C major Sonata K. 545, Beethoven's 5th Symphony finale (in C major). It's the most-played diminished triad in Western music.