The diminished chord formula is 1–♭3–♭5: a root, minor third, and diminished fifth. For example, C diminished contains C–E♭–G♭. Its two stacked minor thirds and six-semitone root-to-fifth span create the tense, unsettled sound associated with diminished harmony.
A diminished chord may be written as Cdim or C°. These symbols describe a triad unless a seventh is explicitly shown.
What Is the Diminished Chord Formula?
The diminished triad formula is 1–♭3–♭5. Start with a major triad, then lower both its third and fifth by one semitone. C major is C–E–G, so lowering E to E♭ and G to G♭ produces C–E♭–G♭.
The interval pattern can also be written as:
- Root to minor third: 3 semitones
- Minor third to diminished fifth: 3 semitones
- Root to diminished fifth: 6 semitones
- Stacked-third pattern: minor third + minor third
The diminished fifth is also called a tritone because it spans three whole tones. Reviewing the diminished fifth interval helps explain why this chord sounds less stable than a major or minor triad.
Bdim provides another useful example. The B major scale begins B–C♯–D♯–E–F♯, so scale degrees 1, ♭3, and ♭5 are B, D, and F. Therefore, Bdim is B–D–F.
How Do You Build a Diminished Chord?
You can build a diminished chord from a major scale, a major triad, or semitone intervals.
Build it from the major scale
Use scale degrees 1, ♭3, and ♭5. For Ddim, begin with D major: D–E–F♯–G–A–B–C♯. Keep D, lower F♯ to F, and lower A to A♭. The result is D–F–A♭.
This method makes the altered degrees visible and connects the formula to other common triad types.
Transform a major triad
A major triad uses 1–3–5. Lower the third and fifth by one semitone:
- Write the major triad.
- Lower its third by one semitone.
- Lower its fifth by one semitone.
- Check that both adjacent intervals are minor thirds.
For F major, F–A–C becomes F–A♭–C♭. Although C♭ sounds like B on an equal-tempered instrument, C♭ is the correct fifth-letter spelling above F. The minor-third interval provides another way to verify each three-semitone step.
Count semitones from the root
Count three semitones above the root for the ♭3, then another three for the ♭5. From A, three semitones reaches C; three more reaches E♭. Adim is therefore A–C–E♭.
Semitone counting is quick, but a correctly spelled triad still uses the root, third, and fifth letters.
What Notes Are in Diminished Chords in Every Key?
The following table applies the 1–♭3–♭5 formula to 12 commonly used roots. Spellings such as C♭, F♭, and double flats preserve each note’s harmonic function.
| Root | Symbol | Formula | Notes |
|---|---|---|---|
| C | Cdim or C° | 1–♭3–♭5 | C–E♭–G♭ |
| D♭ | D♭dim or D♭° | 1–♭3–♭5 | D♭–F♭–A♭♭ |
| D | Ddim or D° | 1–♭3–♭5 | D–F–A♭ |
| E♭ | E♭dim or E♭° | 1–♭3–♭5 | E♭–G♭–B♭♭ |
| E | Edim or E° | 1–♭3–♭5 | E–G–B♭ |
| F | Fdim or F° | 1–♭3–♭5 | F–A♭–C♭ |
| G♭ | G♭dim or G♭° | 1–♭3–♭5 | G♭–B♭♭–D♭♭ |
| G | Gdim or G° | 1–♭3–♭5 | G–B♭–D♭ |
| A♭ | A♭dim or A♭° | 1–♭3–♭5 | A♭–C♭–E♭♭ |
| A | Adim or A° | 1–♭3–♭5 | A–C–E♭ |
| B♭ | B♭dim or B♭° | 1–♭3–♭5 | B♭–D♭–F♭ |
| B | Bdim or B° | 1–♭3–♭5 | B–D–F |
Chord charts sometimes simplify enharmonic spellings. D♭dim may show G instead of A♭♭; both sound alike in equal temperament, but A♭♭ correctly represents the diminished fifth. A guide to how chords are constructed connects interval formulas with note spelling.
How Do Diminished, Diminished 7, and Half-Diminished Chords Differ?
A diminished triad uses 1–♭3–♭5, a fully diminished seventh adds ♭♭7, and a half-diminished seventh adds ♭7. The last interval determines whether the seventh chord is fully or half diminished.
| Chord type | Common symbols | Formula | Notes from C |
| Diminished triad | Cdim, C° | 1–♭3–♭5 | C–E♭–G♭ |
| Fully diminished seventh | Cdim7, C°7 | 1–♭3–♭5–♭♭7 | C–E♭–G♭–B♭♭ |
| Half-diminished seventh | Cm7♭5, Cø7 | 1–♭3–♭5–♭7 | C–E♭–G♭–B♭ |
Why does dim7 use a double-flat seventh?
Chord spelling follows letter order as well as sound. The seventh above C must use some form of B. Lowering the major seventh B by two semitones gives B♭♭, so Cdim7 is C–E♭–G♭–B♭♭. Writing A produces the same piano key but disguises the note’s role as a diminished seventh.
A fully diminished seventh contains four stacked minor thirds and divides the octave into equal segments. C°7, E♭°7, G♭°7, and A°7 can use the same sounding notes; context determines the name and spelling.
Why is m7♭5 called half diminished?
Cm7♭5 contains a diminished triad, C–E♭–G♭, but its B♭ is a minor seventh rather than a diminished seventh. Only the triad portion is diminished, which explains the name “half-diminished.” The distinction is covered in more depth in this guide to diminished chord types and uses.
Why Do Diminished Chords Sound Tense?
Diminished chords sound tense because the diminished fifth divides the octave in half and lacks the stability of a perfect fifth. Their close minor-third spacing also creates strong tendencies for individual notes to move by a semitone into a more stable chord.
Leading-tone resolution
In a major key, a diminished triad occurs naturally on scale degree seven. In C major, the diatonic triads are C, Dm, Em, F, G, Am, and Bdim. Bdim contains B–D–F:
- B rises one semitone to C.
- D may rise to E or fall to C.
- F falls one semitone to E.
Moving B–D–F to C–E–G creates clear voice leading toward the tonic. The pattern becomes easier to recognize when viewed alongside the chords in a major key.
Passing and secondary diminished chords
A diminished chord can create chromatic bass motion. C–C♯dim–Dm produces the rising line C–C♯–D while other voices move smoothly.
A fully diminished seventh can also act as a leading-tone chord aimed at a temporary target. C♯°7 can lead to D minor or D major because C♯ rises to D. The surrounding key and resolution—not the symmetrical shape alone—reveal its function.
How Do Diminished Chords Work on Guitar and Piano?
On guitar and piano, diminished notes may be doubled, inverted, or spread across octaves without changing the chord’s identity.
Guitar voicings
Guitarists often use compact three-note shapes for diminished triads and four-note movable shapes for dim7 chords. A fully diminished seventh shape repeats every three frets because moving each note up three semitones produces another inversion of the same four-note pitch collection. This symmetry does not apply in the same way to a plain three-note diminished triad or m7♭5 chord.
When checking a shape, identify its actual notes instead of relying only on the lowest note. The guitar chord construction process helps separate the chord root from the bass note in inversions.
Piano voicings
On piano, play C–E♭–G♭ for Cdim. E♭ in the bass creates first inversion; G♭ in the bass creates second inversion. For C°7, add B♭♭—the key that also sounds as A.
In an ensemble, players may omit or redistribute notes to avoid a crowded register. Keep the tones that communicate the chord’s function, especially the tendency notes that resolve by semitone.
Frequently Asked Questions
Is a diminished chord the same as a diminished seventh chord?
No. A diminished chord or diminished triad uses 1–♭3–♭5, while a diminished seventh chord uses 1–♭3–♭5–♭♭7. Cdim has three theoretical notes; Cdim7 has four.
What is the difference between diminished and half-diminished chords?
A fully diminished seventh uses a diminished seventh, ♭♭7, while a half-diminished seventh uses a minor seventh, ♭7. C°7 is C–E♭–G♭–B♭♭, whereas Cm7♭5 is C–E♭–G♭–B♭.
Why does a diminished seventh chord use a double flat?
The seventh chord tone must retain the seventh letter name above the root. In Cdim7, that letter is B, and lowering B by two semitones produces B♭♭ rather than A, even though the two notes sound alike in equal temperament.
How many semitones are in a diminished chord?
A diminished triad has three semitones from the root to the minor third and three more to the diminished fifth. The diminished fifth sits six semitones above the root.
Which scale degree forms a diminished chord in a major key?
The seventh scale degree forms a diminished triad in a major key. In C major, B–D–F creates Bdim, which commonly resolves to C major.
Can the same diminished seventh shape represent four chords?
Yes. A fully diminished seventh chord is symmetrical, so one pitch collection can be interpreted from any of its four chord tones. The musical context and resolution determine the most useful root name and theoretical spelling.
Liam Turner is a guitar theory writer and chord analysis specialist at Chord Calculator. He focuses on chord construction, music theory, scale relationships, harmony tools, and guitar learning resources for musicians, producers, songwriters, and beginners. Liam creates practical, easy-to-follow content around chord progressions, interval formulas, key analysis, and interactive music tools to help users better understand harmony, songwriting, and instrument practice.