Chord Finder

How the Chord Finder Works

Every note you enter is first reduced to a pitch class — an integer 0 through 11 representing which of the 12 semitones it is, with octave discarded entirely (C4 and C6 both become pitch class 0). The calculator then tries each unique note in your input as a candidate root, one at a time. For a given candidate root, it measures the semitone distance from that root up to every other note in the chord (wrapping around within one octave), producing a set of intervals. That interval set — always including 0 for the root itself — is compared against a library of known chord formulas. The first root and formula combination that matches exactly is reported as the answer.

Chord Types Recognized

Chord Type	Intervals from Root (semitones)
Major	0, 4, 7
Minor	0, 3, 7
Diminished	0, 3, 6
Augmented	0, 4, 8
Major 7th	0, 4, 7, 11
Dominant 7th	0, 4, 7, 10
Minor 7th	0, 3, 7, 10
Minor 7th flat 5	0, 3, 6, 10
Diminished 7th	0, 3, 6, 9
Sus2	0, 2, 7
Sus4	0, 5, 7

Worked Example: Identifying C Major

Input "C, E, G" reduces to pitch classes 0, 4, and 7. Trying C (pitch class 0) as the root first: E is 4 semitones above C, and G is 7 semitones above C, giving the interval set 0, 4, 7 — an exact match for the Major formula. The calculator stops there and reports "C Major," without needing to try E or G as alternate roots.

Chord Terms You Should Know

Root — the note a chord is built from and named after; C Major's root is C, regardless of which note is played lowest.

Pitch class — a note's identity independent of octave; all the notes called "C," whether C1 or C7, share pitch class 0.

Triad — any three-note chord built from a root, a third, and a fifth — major, minor, diminished, and augmented are all triads.

Inversion — a chord with a note other than the root played as the lowest pitch (e.g. E-G-C is a first-inversion C Major). This calculator identifies the chord regardless of inversion, since note order in your input never matters.

Enharmonic equivalent — two spellings of the same pitch, like C# and Db. This calculator treats them as identical when reading your input, but always reports results using sharp spelling.

Common Chord-Finding Mistakes

Assuming note order in the input changes the result — it never does; a chord is an unordered collection of pitch classes, not a sequence. Another common mix-up: expecting an extended chord (a 9th, 11th, or 13th), an added-tone chord (add9), or a slash chord to match — this calculator's formula library covers only the eleven triad and seventh-chord shapes listed above, so anything outside that set correctly reports no match rather than a wrong guess.

Why Some Chords Won't Match

A "No standard chord match found" result usually means one of three things: the notes form an extended or added-tone chord not in the recognized library, one of the entered notes doesn't actually belong to any simple chord with the others, or a typo was made in one of the note names. Double-check each note's spelling first — a stray letter outside A through G, or an accidental typed with the wrong character, is the most common cause.