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New Released in April 2026

C Diminished Chord on Piano (Cdim)

The C diminished chord (Cdim) on the piano has three notes: C, Eb, Gb. It is a minor triad with a lowered fifth, formula 1 b3 b5, built from two minor thirds. Below: the keyboard, the three positions, how it compares with C and Cm, and where it goes next.

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Cdim C Eb Gb

Cdim on the keyboard: three positions

Any order of C, Eb, Gb is still Cdim.

Cdim C Eb Gb

Root position: C Eb Gb

Cdim Eb Gb C

1st inversion: Eb Gb C

Cdim Gb C Eb

2nd inversion: Gb C Eb

  • Root position: starts on C, a white key; black keys: Eb, Gb
  • 1st inversion: starts on Eb, a black key; black keys: Eb, Gb
  • 2nd inversion: starts on Gb, a black key; black keys: Gb, Eb

Cdim compared with C, Cm and the other triads

Same root, same third or fifth moved by a semitone.

ChordNotesThirdFifth
C C E Gmajor 3rdperfect 5th
Cm C Eb Gminor 3rdperfect 5th
Cdim C Eb Gbminor 3rddiminished 5th
Caug C E G#major 3rdaugmented 5th

What Cdim does in music

  • Cdim is the vii° chord of Db major and the ii° chord of Bb minor.
  • It wants to move up a semitone: Cdim → Db / Dbm, the bottom note rising to the new root.
  • Add Bb and you get Cm7b5 (half-diminished); add Bbb instead and you get Cdim7 (diminished 7th).

Cm7b5 · Db

ChordRunner showing a chord block while hands play the piano

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In ChordRunner Cdim rides towards your runner between other chords: play it in time. MIDI keyboard or microphone, both work.

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All piano chords · Diminished chords explained

Common questions

What notes are in the C diminished chord?

Cdim has three notes: C, Eb, Gb. Root, minor 3rd and diminished 5th (formula 1 b3 b5).

What is the difference between Cdim and Cm?

One note. Cm has G on top; Cdim moves it to Gb. The new fifth is what gives Cdim its tense sound.

Where does Cdim go?

Cdim is the vii° chord of Db major and the ii° chord of Bb minor. It wants to move up a semitone: Cdim → Db / Dbm, the bottom note rising to the new root.

Can I practise Cdim with a MIDI keyboard or microphone?

Yes. ChordRunner detects a USB MIDI keyboard automatically and also hears an acoustic piano through the microphone. Cdim counts in any position, as long as C, Eb, Gb sound together.

Your instrument is the controller.

ChordRunner is a browser game that teaches piano and guitar chords: a chord appears on screen, you play it on a real instrument, and your runner jumps. MIDI keyboard or microphone, both work.

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