Chord Calculator (notes in any chord: triads, 7ths, 6ths, 9ths)

Understanding the chord calculator — concept and principle

This calculator lists the notes of a chord from its root and type, with correct spelling, the chord symbol, the intervals and the semitone distances. Use it to learn chord construction, write out voicings, check a lead sheet, or find notes on an unfamiliar instrument.

How it is calculated

A chord is a stack of intervals above the root. Each interval has two parts:

• a degree, which says how many letter names to count (3rd = two letters up, 5th = four letters up, 7th = six letters up);
• a size in semitones (minor 3rd = 3, major 3rd = 4, perfect 5th = 7, minor 7th = 10, major 7th = 11, major 9th = 14).

For each chord tone the calculator moves up the right number of letters from the root, then adds ♯ or ♭ until the note is the right number of semitones above the root. Intervals are labelled against the root's major scale, so ♭3 means a minor 3rd and ♭♭7 a diminished 7th.

The principle

Western harmony builds chords mainly in thirds. A major triad is a major 3rd plus a minor 3rd (4 + 3 semitones), a minor triad the reverse (3 + 4). Adding another third gives a seventh chord. Counting letters first and semitones second keeps each note in its proper role. Without that, E♭ minor might come out as D♯–F♯–A♯, which sounds the same but reads as a different chord on paper. Sixth, added-ninth and suspended chords follow the same idea with different degrees: sus4 replaces the 3rd with a 4th, and add9 adds a 9th (a 2nd an octave up) without the 7th.

Worked example

Default inputs: root C, Major 7th.

1. The major 7th pattern is root, major 3rd (4), perfect 5th (7), major 7th (11).
2. 3rd: two letters up from C is E, 4 semitones above C, so E with no accidental.
3. 5th: four letters up is G, 7 semitones, so G.
4. 7th: six letters up is B, 11 semitones, so B.
5. Result: C – E – G – B, symbol Cmaj7, intervals 1 – 3 – 5 – 7, semitones 0 – 4 – 7 – 11, 4 notes.

How to read the result

The notes are listed in stacked order from the root, which is root position. You can play them in any octave or order; the lowest note decides the inversion. The interval line tells you the chord's character at a glance: a ♭3 makes it minor, a ♭5 diminished, a ♭7 dominant or minor seventh.

Common mistakes

• Spelling by sound only, for example writing F♯m as G♭m in a sharp key.
• Confusing maj7 (11 semitones) with 7 (10 semitones).
• Treating sus chords as major or minor; they have no 3rd.

Frequently asked questions

What notes are in a C major 7th chord?

C, E, G and B: a major triad with a major 7th on top.

What is the difference between C7 and Cmaj7?

C7 has B♭, a minor 7th (10 semitones); Cmaj7 has B, a major 7th (11 semitones).

Why does a diminished 7th chord show a double flat?

The diminished 7th sits a semitone below a minor 7th. Above C that is B♭♭, which sounds like A but keeps the chord spelled in thirds.

Sources: S. Kostka, D. Payne & B. Almén, Tonal Harmony, 8th ed. (McGraw-Hill, 2018), ch. 1–4 · M. Levine, The Jazz Theory Book (Sher Music, 1995), ch. 1–2