Diminished Chords on Guitar
Updated · The Acoustic Guitarist
A diminished triad stacks two minor 3rds, 1 ♭3 ♭5, so Cdim is C E♭ G♭. A diminished 7th adds a third minor 3rd, 1 ♭3 ♭5 𝄫7, so Cdim7 is C E♭ G♭ B𝄫. The 7th chord is symmetrical: every note is 3 frets from the next, so one shape repeats up the neck.
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What a diminished chord is
A minor chord is root, minor 3rd and perfect 5th (1 ♭3 5). A diminished chord lowers the 5th as well, so the formula is 1 ♭3 ♭5. Stack two minor 3rds on the root and you get it. Cdim is C E♭ G♭.
The symbol is dim or a small circle. Cdim and C° mean the same chord. Both have a tight, dark, unresolved sound that wants to move on.
| Chord | Formula | Notes |
|---|---|---|
| Bdim | 1 ♭3 ♭5 | B D F |
| Cdim | 1 ♭3 ♭5 | C E♭ G♭ |
| F♯dim | 1 ♭3 ♭5 | F♯ A C |
| Adim | 1 ♭3 ♭5 | A C E♭ |
The diminished 7th chord
Add one more minor 3rd on top and the chord has four notes: 1 ♭3 ♭5 𝄫7. The top note is a double-flat 7th, one half step below the usual ♭7. Cdim7 is C E♭ G♭ B𝄫, and B𝄫 is the same pitch as A. You will also see it written C°7.
The extra letter does not change the sound much, but it matters for the name. On a chart, dim means the triad, and dim7 means the four-note chord.
Diminished 7th vs half-diminished
Three chords share the same triad:
| Chord | Formula | Notes |
|---|---|---|
| Cdim | 1 ♭3 ♭5 | C E♭ G♭ |
| Cm7♭5 (half-diminished) | 1 ♭3 ♭5 ♭7 | C E♭ G♭ B♭ |
| Cdim7 | 1 ♭3 ♭5 𝄫7 | C E♭ G♭ B𝄫 |
The half-diminished chord has a minor 7th and sounds softer and more jazzy. The full diminished 7th has the lower 7th and sounds tighter and more dramatic. The half-diminished 7th guide covers the first one in detail.
Where the diminished triad lives
In any major key, the diminished chord is built on the 7th degree, written vii°. It is the only diminished triad in the scale.
- In C major it is Bdim (B D F).
- In G major it is F♯dim (F♯ A C).
It is made of the 7th, 2nd and 4th notes of the scale, and that makes it a stand-in for a V7 chord. B D F sits inside G7 (G B D F), so Bdim pulls toward C the way G7 does. The key of C major page shows all seven chords in one key.
Diminished shapes on guitar
The strings from low to high are E A D G B E. Below, x means do not play the string and the numbers are frets, written from the 6th string to the 1st.
- Bdim (x 2 3 4 3 x): root on the 5th string. The shape is four strings wide, so mute the 6th and 1st.
- Cdim (x 3 4 5 4 x): the Bdim shape slid up one fret. The root is still the lowest note.
- Cdim7 (x 3 4 2 4 x): the shape most guitarists learn first. It has four strings and four different notes.
- Adim7 (x 0 1 2 1 2): an open A, then D♯, A, C and F♯. Five notes of a four-note chord, since A is doubled.
Since each shape has no open strings (except Adim7), you can slide it to any fret and the name follows the lowest note.
Why dim7 shapes repeat every 3 frets
The notes of a dim7 chord are 3 semitones apart: C, E♭, G♭, A, and back to C. The four notes split the octave into four equal parts. That has three consequences:
- Four names for one chord. Cdim7, E♭dim7, G♭dim7 and Adim7 have the same four pitches. Any note can be called the root.
- Only three different dim7 chords. Cdim7, C♯dim7 and Ddim7 cover every possibility. Every other dim7 chord is one of these three with a new name.
- One shape, 3 frets. Move x 3 4 2 4 x up 3 frets and you get x 6 7 5 7 x, which has the same four notes in a new order.
Compare this with the augmented chord, which does the same trick with three notes spaced 4 frets apart.
How to use diminished chords
As a passing chord between two chords a whole step apart
The most common use is a half-step bass climb. C♯dim7 is C♯ E G B♭. Play C, then C♯dim7, then Dm: the bass climbs C, C♯, D and each chord leads to the next. The C♯dim7 shape is the Cdim7 shape moved up 1 fret (x 4 5 3 5 x).
As a stand-in for a dominant chord
A dim7 chord is the upper four notes of a dominant 7th with a flat 9th. Bdim7 (B D F A♭) holds the same notes as G7♭9 without the G. That is why Bdim7 resolves strongly to C. When a chart shows a dim7 chord, listen for the chord it leads to.
Quick practice
- Learn Bdim and Cdim7 first. Play each with a steady strum, four strings only.
- Slide Cdim7 up 3 frets three times and listen to the colour stay the same.
- Play C, C♯dim7, Dm slowly. Use the chord finder to check any shape you invent.
- For the 4-note chords that include a 7th, the 7th chord guide sets out the family.
FAQ
What is a diminished chord on guitar?
A chord built from minor 3rds. The triad is 1 ♭3 ♭5, so Bdim is B D F. It sounds tense and unstable and usually leads into a more settled chord. It is written dim or °.
What is a diminished 7th chord?
A diminished triad plus a diminished 7th, 1 ♭3 ♭5 𝄫7. Cdim7 is C E♭ G♭ B𝄫, and B𝄫 sounds the same as A. All four notes are a minor 3rd (3 frets) apart.
What is the difference between diminished 7th and half-diminished?
Both start with a diminished triad. A diminished 7th adds a note one half step lower than the half-diminished 7th. Cdim7 is C E♭ G♭ B𝄫, and Cm7♭5 (half-diminished) is C E♭ G♭ B♭.
Where is the diminished chord in a major key?
On the 7th degree, written vii°. In C major it is Bdim (B D F), and in G major it is F♯dim (F♯ A C).
How many different diminished 7th chords are there?
Only three. Cdim7, E♭dim7, G♭dim7 and Adim7 have the same four pitches, and the same is true of the other two groups. Moving a dim7 shape up 3 frets gives the same chord.