How this calculator works
A chord is a set of pitch classes, so the octave of each note does not matter for the chord name. The page takes the distinct notes you entered and compares the set with every chord recipe on every root, from major and minor triads through suspended chords, sixths, sevenths and extended chords. A set can match more than one chord: the notes C, E, G and A are both C major with an added sixth and A minor seventh, and which name is right depends on the bass and the context. The first row is the most likely reading, and the known root field puts the likely root first.
Formula
for a root r, a chord with intervals i1, i2, ... has the pitch classes (r + i1) mod 12, (r + i2) mod 12, and so on. The chord matches when that set equals the set of notes played. Every root and every chord type is tried, and matches are listed with the chosen root first.
Worked example
The notes C, E and G match C major. The notes C, E, G and A match both C6 and Am7, because their pitch classes are the same set. If you know the bass is A, choose A as the root and the first row becomes Am7. Adding a note usually narrows the list: C, E, G and Bb matches C7 and no longer matches C major.
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Frequently asked questions
Why do several chords fit the same notes?
Chords are sets of pitch classes and many sets are shared. C6 and Am7 contain exactly the same four notes, though they are voiced and function differently. The bass note and the surrounding progression usually settle the question, which is why the known root field is useful.
Why does the octave not matter?
An inversion or a spread voicing uses the same pitch classes, so the chord name is unchanged. What changes is the bass and the arrangement. If you need the inversion, use the chord inversion page after finding the chord.
Why is a power chord not listed?
A power chord is two notes, the root and the fifth, which is not a triad under this naming system. Enter a full triad, or add the fifth and read the result as a chord with an omitted third. Some genres treat the fifth as enough, but harmony theory does not.
Does the spelling field change the chord?
No. It changes how the root is written: the same pitch comes out as C# or Db. Choose the spelling that fits the key you are playing in, and the chord tones follow it.