What Is a Half-Diminished 7th Chord?
A half-diminished 7th chord is a diminished triad with a minor 7th added above the root. It's "half" diminished because the 7th is minor (not diminished like in a fully diminished 7th chord) — this softens the extreme tension of the full diminished 7th.
Also written as m7♭5 (minor 7th flat 5), this chord is a fundamental sound in jazz and classical music. It most commonly appears as the ii chord in minor key progressions.
How to Build a Half-Diminished 7th Chord
Formula
Root + Minor 3rd + Diminished 5th + Minor 7th
Semitones: 0 — 3 — 6 — 10
Example: C Half-Diminished 7th
- C (root)
- E♭ (3 semitones = minor third)
- G♭ (6 semitones = diminished fifth)
- B♭ (10 semitones = minor seventh)
Half vs. fully diminished: Half-diminished has a minor 7th (B♭ in Cø7). Fully diminished has a diminished 7th (B♭♭ = A in C°7). That one semitone difference dramatically changes the character.
All 12 Half-Diminished 7th Chords
| Chord | Root | Minor 3rd | Dim. 5th | Minor 7th |
|---|---|---|---|---|
| Cø7 | C | E♭ | G♭ | B♭ |
| Gø7 | G | B♭ | D♭ | F |
| Dø7 | D | F | A♭ | C |
| Aø7 | A | C | E♭ | G |
| Eø7 | E | G | B♭ | D |
| Bø7 | B | D | F | A |
| F#ø7 | F# | A | C | E |
| Fø7 | F | A♭ | C♭ | E♭ |
| B♭ø7 | B♭ | D♭ | F♭ | A♭ |
| E♭ø7 | E♭ | G♭ | B♭♭ | D♭ |
| A♭ø7 | A♭ | C♭ | E♭♭ | G♭ |
| D♭ø7 | D♭ | F♭ | A♭♭ | C♭ |
The Sound of a Half-Diminished 7th Chord
Tense, dark, sophisticated, unresolved, jazz-flavoured.
The half-diminished 7th has a distinctive sound — darker than a minor 7th but less harshly tense than a fully diminished 7th. It sounds incomplete and forward-moving, which is exactly why it works so well as a ii chord leading to a V7.
Half-Diminished in Minor Key ii-V-i
The half-diminished 7th is the ii chord in minor key progressions. Compare to the major key:
Major key ii-V-I: Dm7 → G7 → Cmaj7
Minor key ii-V-i: Dø7 → G7 → Cm(Maj7)
The half-diminished replaces the minor 7th as the ii chord, giving the minor ii-V-i its characteristic dark tension.
How to Use Half-Diminished 7th Chords
1. As the ii chord in minor: iiø7-V7-im is the minor key ii-V-i. Essential in jazz ballads in minor keys.
2. As a passing chord: Move between two adjacent chords using a half-diminished as a chromatic connector.
3. In jazz standards: "Autumn Leaves," "Stella by Starlight," and many other standards use half-diminished chords prominently.
4. In classical music: The leading-tone 7th chord in a minor key is often a half-diminished.
Free: Chord Ear Training Cheat Sheet
Learn to hear the dark, forward-moving quality of the half-diminished 7th chord.