Chord Identifier
Identify a chord from its notes, or build a named chord from a root and a quality — in 12-tone equal temperament. Enter the notes of a chord (e.g. C E G or Eb G Bb D, with optional octaves like C4 E4 G4) to name it: the tool tries every note as a possible root, matches the interval stack against the standard chord formulas (major, minor, diminished, augmented, suspended, 6ths, 7ths, 9ths, 11ths, 13ths and their variants), reports the chord name with slash-notation inversion when octaves are given, and shows every alternative spelling for symmetric chords like augmented and diminished-7th. Or go the other way: pick a root and a chord type to list the notes, the interval formula, and the scale-degree of each tone. Everything runs locally in your browser.
Identify a chord (notes → name)
Build a chord (name → notes)
The math. A chord is a stack of pitch classes measured in semitones from a root. Each chord quality has a fixed interval formula — a major triad is {0, 4, 7} (root, major 3rd, perfect 5th), a minor triad {0, 3, 7}, a dominant 7th {0, 4, 7, 10}, and so on, with 9ths/11ths/13ths collapsing to the same pitch classes as 2nds/4ths/6ths (mod 12). To identify a chord, the tool normalises every entered note to a pitch class 0–11, then for each candidate root rotates the set so the root maps to 0 and looks the sorted interval stack up in the formula table. A match found with the lowest entered note as the root is root position; if another chord tone is in the bass (computed when octaves are supplied) the chord is an inversion, written in slash notation as C/E (C major with E in the bass). Symmetric chords have several equally-valid roots: the augmented triad repeats every 4 semitones and the diminished 7th every 3, so all such roots are listed. Enharmonic equivalents (C♯ = D♭) are the same pitch class; the ♯/♭ toggle only changes spelling. Pairs with the Scale & Key Generator and the Note Frequency Calculator. Everything runs locally — nothing leaves your browser.