Why does my chord have more than one name?

Because some sets of notes genuinely do. A diminished seventh is four notes spaced three semitones apart, so any of the four can be heard as the root: C Eb Gb A is C diminished seventh, A diminished seventh, F# diminished seventh and D# diminished seventh, all correct. An augmented triad divides the octave into three and has three names the same way. The page lists every reading in inversion order, so the one whose root is the key you are holding at the bottom comes first.

How does it work out the inversion?

From the lowest key held. C E G is C major in root position; press E G C instead and it is the same chord in first inversion, with E in the bass. Octave doubling changes nothing: the naming is by pitch class, so C3 with C4, E4 and G4 is still a three-note C major, and the page lists the four keys you are holding while counting three notes.

Which chords does it know?

Twelve formulas, printed in full under the keyboard: the four triads (major, minor, diminished, augmented) and eight sevenths (dominant, major, minor, minor major, half-diminished, diminished, augmented, augmented major). Sixths, ninths and suspended chords are outside that set on purpose, so the matching stays exact. A set that is not one of the twelve is reported as unmatched, with any formula it is a single note away from named, rather than being rounded to the nearest chord.

Why does it print Bbb rather than A?

Because the notes are spelled by scale degree from the root of that reading. The seventh of a C chord has to be a kind of B, so C diminished seventh is C Eb Gb Bbb. It is the same key on the piano either way, and the keyboard highlights it as the A key. Where a root has two usable spellings the page writes the one a musician writes, Db major rather than C# major, C# minor rather than Db minor, and prints the other name beside it.

Can I go the other way, from a chord name to the keys?

Yes. Switch to From a name, pick a root, a chord type and an inversion, and the keys light up on the keyboard with the notes, the degrees and the voicing beside them. The spelling you pick is the one you get: C# major is written C# E# G#, Db major is written Db F Ab, and they are the same three keys.

Does it work on a phone, and with a keyboard instead of a mouse?

Yes. Every piano key is a button in the tab order, so you can move to one and press it with the keyboard, and each black key tells a screen reader both of its names, such as C sharp 3, also D flat 3. On a narrow screen the two octaves scroll sideways rather than shrinking to nothing.

Is anything uploaded or kept?

Nothing is uploaded. The matching runs in this browser and what you played is never sent anywhere. The mode, the keys you were holding and the chord you were building are saved on this device alone so they are still there next visit, and the Start over button above the tool forgets them.

Piano Chord Finder

Press keys on the two octaves below, from C3 to B4, and the page names the chord on the first screen: the notes, the scale degrees, the inversion taken from the lowest key you are holding, and the voicing you actually played. Where a set of keys has more than one correct name, which happens whenever the notes divide the octave evenly, every reading is listed rather than one being chosen for you: a diminished seventh has four names and an augmented triad has three. It works the other way too, from a root and a chord type to the keys, and when a set matches none of the twelve formulas the page prints, it says so, and names any formula the set is a single note away from.

C E G3 notesroot position

selectedC4 E4 G4

C majorC E Groot position

degrees1 3 5

other namesnone: this set has one reading

Chord

C major

Notes

C E G

Inversion

root position

Intervals

1 3 5

C major, root position. Notes C E G, degrees 1 3 5. No other formula on this page fits these notes.

Way in

Root

Chord type

Inversion

One name fits these keys.

CC majorC E Groot position, bass C

C E Gthree notes
C major, root position
E G Cthe same notes
C major, first inversion
C Eb Gb Afour notes
C diminished seventh, root position, 4 names in all

The formulas this page matches against

Four triads and eight sevenths, each written as the scale degrees it is built from and the semitones those degrees are above the root. A set of keys is named only when its pitch classes equal one of these exactly.

Chord	Symbol	Degrees	Semitones	On C
major	C, with nothing after it	1 3 5	0 4 7	C E G
minor	Cm	1 b3 5	0 3 7	C Eb G
diminished	Cdim	1 b3 b5	0 3 6	C Eb Gb
augmented	Caug	1 3 #5	0 4 8	C E G#
dominant seventh	C7	1 3 5 b7	0 4 7 10	C E G Bb
major seventh	Cmaj7	1 3 5 7	0 4 7 11	C E G B
minor seventh	Cm7	1 b3 5 b7	0 3 7 10	C Eb G Bb
minor major seventh	Cm(maj7)	1 b3 5 7	0 3 7 11	C Eb G B
half-diminished seventh	Cm7b5	1 b3 b5 b7	0 3 6 10	C Eb Gb Bb
diminished seventh	Cdim7	1 b3 b5 bb7	0 3 6 9	C Eb Gb Bbb
augmented seventh	C7#5	1 3 #5 b7	0 4 8 10	C E G# Bb
augmented major seventh	Cmaj7#5	1 3 #5 7	0 4 8 11	C E G# B

Why a double flat turns up. Notes are spelled by scale degree from the root of the reading, so C diminished seventh prints C Eb Gb Bbb: its seventh has to be a kind of B. The key you press is the same one either way, and the other spelling of a root is printed beside the name whenever there is one.

Up to 10 keys at once, across two octaves from C3 to B4, read here in your browser with nothing uploaded and no account. The mode, the held keys and the chord you were building are kept in this browser alone, and the Start over button above the tool forgets them.

Accuracy. Exact matching against the chord formulas written on this page, by pitch class. A symmetrical set such as a diminished seventh genuinely has more than one correct name, and the page lists them all rather than choosing one for you.

Common questions

Why does my chord have more than one name?: Because some sets of notes genuinely do. A diminished seventh is four notes spaced three semitones apart, so any of the four can be heard as the root: C Eb Gb A is C diminished seventh, A diminished seventh, F# diminished seventh and D# diminished seventh, all correct. An augmented triad divides the octave into three and has three names the same way. The page lists every reading in inversion order, so the one whose root is the key you are holding at the bottom comes first.
How does it work out the inversion?: From the lowest key held. C E G is C major in root position; press E G C instead and it is the same chord in first inversion, with E in the bass. Octave doubling changes nothing: the naming is by pitch class, so C3 with C4, E4 and G4 is still a three-note C major, and the page lists the four keys you are holding while counting three notes.
Which chords does it know?: Twelve formulas, printed in full under the keyboard: the four triads (major, minor, diminished, augmented) and eight sevenths (dominant, major, minor, minor major, half-diminished, diminished, augmented, augmented major). Sixths, ninths and suspended chords are outside that set on purpose, so the matching stays exact. A set that is not one of the twelve is reported as unmatched, with any formula it is a single note away from named, rather than being rounded to the nearest chord.
Why does it print Bbb rather than A?: Because the notes are spelled by scale degree from the root of that reading. The seventh of a C chord has to be a kind of B, so C diminished seventh is C Eb Gb Bbb. It is the same key on the piano either way, and the keyboard highlights it as the A key. Where a root has two usable spellings the page writes the one a musician writes, Db major rather than C# major, C# minor rather than Db minor, and prints the other name beside it.
Can I go the other way, from a chord name to the keys?: Yes. Switch to From a name, pick a root, a chord type and an inversion, and the keys light up on the keyboard with the notes, the degrees and the voicing beside them. The spelling you pick is the one you get: C# major is written C# E# G#, Db major is written Db F Ab, and they are the same three keys.
Does it work on a phone, and with a keyboard instead of a mouse?: Yes. Every piano key is a button in the tab order, so you can move to one and press it with the keyboard, and each black key tells a screen reader both of its names, such as C sharp 3, also D flat 3. On a narrow screen the two octaves scroll sideways rather than shrinking to nothing.
Is anything uploaded or kept?: Nothing is uploaded. The matching runs in this browser and what you played is never sent anywhere. The mode, the keys you were holding and the chord you were building are saved on this device alone so they are still there next visit, and the Start over button above the tool forgets them.

Exact matching against the chord formulas written on this page, by pitch class. A symmetrical set such as a diminished seventh genuinely has more than one correct name, and the page lists them all rather than choosing one for you.