🎹 Chord Builder

Select a root note and chord type to see the notes that make up the chord.

Chords are counted in semitones from the root

Every chord type here is a fixed list of semitone steps above the root, looked up in the twelve-note chromatic scale and wrapped back round at the octave:

note = NOTES[(root index + semitones) mod 12]

major 0-4-7    minor 0-3-7    diminished 0-3-6    augmented 0-4-8
maj7  0-4-7-11 min7  0-3-7-10 dom7        0-4-7-10

C major is index 0, so 0, 4 and 7 give C - E - G: the root, a major third of four semitones, and a perfect fifth of seven. Lower that third by a semitone and the chord turns minor; stretch the fifth to eight and it is augmented.

The seven types side by side

TypeSemitonesIntervalsOn C
Major0-4-7R, M3, P5C E G
Minor0-3-7R, m3, P5C D# G
Diminished0-3-6R, m3, d5C D# F#
Augmented0-4-8R, M3, A5C E G#
Major 7th0-4-7-11R, M3, P5, M7C E G B
Minor 7th0-3-7-10R, m3, P5, m7C D# G A#
Dominant 7th0-4-7-10R, M3, P5, m7C E G A#
Everything is named with sharps, so there are no flats in the root list either - ask for A# rather than Bb, which is the same pitch. The notes are also given in root position and in one octave; how you voice or invert them is up to you.

Frequently asked questions

What notes are in a C major chord?

C, E and G. Count four semitones up from C for the major third and seven for the perfect fifth. The same shape from G gives G, B and D.

What is the difference between a major 7th and a dominant 7th chord?

One semitone at the top. Cmaj7 stacks an 11-semitone major seventh for C E G B, while C7 uses a 10-semitone minor seventh for C E G A#. The first is restful, the second pulls towards F.

Why does C minor show D# and not Eb?

The tool spells the whole chromatic scale with sharps. D# and Eb are the same key on a piano, though written music prefers Eb so the chord uses the letters C, E and G - one per third in the stack. Read D# as Eb, D# G A# as Eb G Bb, and so on.