Diminished Chord

To make a diminished chord with three notes, start on any piano key and stack two three-semitone steps. From C, that gives C–E♭–G♭: the formula 1 ♭3 ♭5.

Highlighted keys show a close root-position example. Keyboard labels use simple sharp names; the formula uses theoretical spelling. E♭ and D♯, for example, share a piano key in equal temperament.

Build it by counting the gaps

1. Choose a starting note. Count adjacent piano keys, including black keys, as one semitone per move.
2. Move up three semitones for the minor third. Move up another three for the diminished fifth.
3. Play the three selected pitches together. The distance from the first note to the last is six semitones, not three.

A minor chord keeps a perfect fifth, seven semitones above its root. Lowering that fifth by one semitone produces the diminished triad. For C, compare C–E♭–G with C–E♭–G♭. Changing the fifth leaves the minor third in place.

Three related names, three different note sets

Keep the root fixed in the tool and change Type. The triad stays underneath both seventh-chord versions; what changes is whether a fourth tone is present, and which seventh it is.

Read dim7 or °7 as fully diminished seventh, and m7♭5 or ø7 as half-diminished seventh. An unqualified “dim” can be shorthand in an arrangement; this tool uses it specifically for the triad. When a score uses shorthand, check its notes or the arranger’s convention.

The seventh of Cdim7 is written B♭♭ because it is two semitones below C major’s seventh, B. It sounds as A. Writing the interval correctly helps distinguish it from the B♭ of Cm7♭5.

Hear it in a musical context

In C major, notes B–D–F form the diminished triad on the seventh scale degree. B can rise to C and F can fall to E as the music reaches a C-major harmony; the remaining voices depend on the chosen voicing. Those short movements help explain a common feeling of tension followed by release.

A diminished chord can also connect harmonies or take part in a change of key. It is not restricted to a single emotional effect, and replacing a chord is not automatically successful: the melody, bass and surrounding progression still matter.

Why a diminished seventh can have several names

A complete dim7 pitch-class set divides an octave into equal three-semitone gaps. Cdim7 contains the pitches C, E♭, G♭ and A; choosing another member as the named root can describe the same piano keys with a different spelling. The intended key and musical function help decide which name to write.

The three-note diminished triad and half-diminished seventh do not have that complete four-part symmetry. Transposing either by three semitones generally produces a different pitch-class set. Changing a voicing’s register also changes its actual sound, even when its pitch classes are preserved.

diminished chords

Every major scale steps 0, 2, 4, 5, 7, 9, 11 semitones from its tonic. Its vii° is scale degrees 7, 2 and 4. Every natural minor scale steps 0, 2, 3, 5, 7, 8, 10 semitones. Its ii° is scale degrees 2, 4 and 6. Every row below is 0, 3, 6 semitones from its own root. The tables use the usual names for the twelve keys.

The C major row is B, D, F, the same three notes already named in the section above. A minor's ii° is also B, D, F: A is 3 semitones under C, and both rows were taken from their own scales.

Put C major's vii° in close position as B4, D5, F5. B4 is MIDI 71, D5 is 74 and F5 is 77. The lowest note's distance from B4 is the inversion: root position 71 − 71 = 0, degree 1; first inversion 74 − 71 = 3, degree ♭3; second inversion 77 − 71 = 6, degree ♭5.

From B4–D5–F5 toward C major, B4 to C5 is 72 − 71 = 1 semitone and F5 to E5 is 76 − 77 = −1. D5 can go to C5, 72 − 74 = −2, or to E5, 76 − 74 = 2. The outer interval changes from 77 − 71 = 6 semitones to 76 − 72 = 4.

Take the notes to your instrument

This page explains the note relationships. For string positions, silent strings and fret-by-fret checks, continue to diminished chord guitar. The two pages use the same chord formulas; the guitar page answers how to place those notes on a fretboard.

Is diminished the same as minor?

No. Both triads have a minor third, but the diminished triad lowers the fifth. That difference changes the note set and how it interacts with other parts.

Does “half diminished” mean half the notes?

No. A half-diminished seventh still has four distinct chord tones. Its name distinguishes its minor seventh from the diminished seventh in a fully diminished chord.