Diminished 7th Chords on Piano
The diminished 7th chord is a symmetrical four-note chord built entirely from minor thirds — dividing the octave into four equal parts. It is the most dramatic and tense chord in tonal music, used for suspense, modulation, and classical cadences.
Formula: Root – Minor 3rd – Diminished 5th – Diminished 7th
Intervals: 3 + 3 + 3 semitones (three stacked minor thirds)
Scale degrees: 1–♭3–♭5–°7
Sound: Dramatic, tense, suspenseful, urgent
Symbol: dim7 or °7 (Cdim7, C°7)
Perfect symmetry: Because dim7 divides the octave into four equal parts, there are only three unique diminished 7th chords. Cdim7, E♭dim7, G♭dim7, and Adim7 all contain the same four notes. This makes dim7 the ultimate pivot chord — it can resolve to any of four different keys, making it invaluable for key changes.
Diminished 7th Chord in All 18 Keys
C Diminished 7th Chord
C# Diminished 7th Chord
Db Diminished 7th Chord
D Diminished 7th Chord
D# Diminished 7th Chord
Eb Diminished 7th Chord
E Diminished 7th Chord
F Diminished 7th Chord
F# Diminished 7th Chord
Gb Diminished 7th Chord
G Diminished 7th Chord
G# Diminished 7th Chord
Ab Diminished 7th Chord
A Diminished 7th Chord
A# Diminished 7th Chord
Bb Diminished 7th Chord
B Diminished 7th Chord
Cb Diminished 7th Chord