You stumble onto a great-sounding shape, but you have no idea what to call it. Identifying a chord isn't guesswork — every chord name is just a description of the intervalsstacked above its root note. Learn that logic and you can name almost any chord on sight.
This guide shows you how chords get their names, how to work out a chord from the notes you're fretting, how to tell major from minor from 7th, and how to read a chord straight off a diagram.
Identify a chord in 30 seconds
Name every note you're fretting, drop the duplicates, then stack them in thirds. The bottom of that stack is the root — it gives the chord its letter. Measure up from the root: a major 3rd (4 frets) = major, a minor 3rd(3 frets) = minor. A flat 7th on top makes it a dominant 7th. When in doubt, drop the notes into a guitar chord finder to confirm.
How Chords Are Named From Intervals
A chord is a stack of notes built in thirds above a starting note called the root. The root gives the chord its letter name — a chord rooted on C is some kind of "C chord." Everything after that letter describes the intervals piled on top.
The three core building blocks of a basic chord (a triad) are:
- Root (1): the foundation note that names the chord.
- Third (3): two letters up from the root — decides major vs minor.
- Fifth (5): the stabilizing note, a perfect 5th (7 half steps) above the root.
Add a fourth note a third above the fifth and you get a 7th chord. Keep stacking and you reach 9ths, 11ths and 13ths. The name simply lists what's there. For the full system, see our guitar chord theory guide.
Root, 3rd, 5th, and 7th: The Defining Intervals
The distance from the root to each chord tone is what determines the chord type. Here are the intervals you'll meet most often, measured in half steps (frets) above the root:
| Chord tone | Interval | Half steps |
|---|---|---|
| Minor 3rd | b3 | 3 |
| Major 3rd | 3 | 4 |
| Diminished 5th | b5 | 6 |
| Perfect 5th | 5 | 7 |
| Minor (flat) 7th | b7 | 10 |
| Major 7th | 7 | 11 |
Notice the only difference between a major and minor 3rd is one half step — one fret. That single fret is the most important distinction in all of chord identification. If you're not yet confident measuring intervals, work through our guitar interval training guide first.
Major vs Minor vs 7th Chords
Once you know the intervals, the common chord types are easy to recognize. Using C as the root:
- Major (C): root + major 3rd + perfect 5th → C E G. Bright, resolved.
- Minor (Cm): root + minor 3rd + perfect 5th → C Eb G. The 3rd is one fret lower than major.
- Dominant 7th (C7): major triad + flat 7th → C E G Bb. Bluesy, restless.
- Major 7th (Cmaj7): major triad + major 7th → C E G B. Lush, jazzy.
- Minor 7th (Cm7): minor triad + flat 7th → C Eb G Bb. Smooth, mellow.
The pattern to memorize: the 3rd sets the mood (major/minor), and the 7th adds color. A "C7" and a "Cmaj7" share the same triad — only the type of 7th separates them. Browse and hear all of these shapes side by side in our guitar chord library.
Identifying a Chord From the Notes You're Fretting
Here's the practical process in action. Say you're holding a shape and the sounding notes are A, C, and E:
- List the unique notes: A, C, E.
- Stack them in thirds: A → C → E already lines up, so the root is A.
- Measure the 3rd: A to C is 3 half steps — a minor 3rd. So this is a minor chord.
- Measure the 5th: A to E is 7 half steps — a perfect 5th. Confirmed triad.
- Result: A minor (Am).
Add a G to that shape (A C E G) and you'd measure A to G as 10 half steps — a flat 7th — giving you A minor 7th (Am7). The same method scales up to any chord: name, dedupe, stack, measure.
To do this instantly, use a guitar chord finder to select your frets and read back the chord name — perfect for confirming your own analysis or when a shape has too many notes to stack by hand.
Reading a Chord From a Diagram
Chord diagrams (chord boxes) are a shorthand for the exact notes you play. To identify the chord:
- Read each dot as a fretted note — note its string and fret.
- Include open strings marked with an O above the nut.
- Skip muted strings marked with an X — they don't sound.
- Translate each position to a note name using the fretboard.
- Stack the notes in thirds and apply the same root/3rd/5th/7th analysis above.
For a full walkthrough of the symbols — dots, finger numbers, barre lines, Xs and Os — see our guide to reading chord diagrams. And if you're unsure of a note's name, the interactive fretboard will label any fret for you.
Inversions, Slash Chords, and Context
Identification gets subtle when the lowest note isn't the root. If you play C major with E in the bass (E G C), the notes still spell C major — but it's a first inversion, often written C/E (a slash chord). The chord is still "C," just voiced with a different bass note.
The same notes can even imply different chords depending on context. C–E–G is plainly C major, but played under an A bass and a busy A-minor passage, those same notes function as part of A minor 7th. When a chord is ambiguous, two things resolve it: the bass note (usually the strongest candidate for the root) and the surrounding key. A chord identifier will typically show you these alternative names so you can pick the one that fits the music.
Practice this with real shapes: pick chords from the chord library, name their notes, then verify your reasoning in the guitar chord finder. Do it a dozen times and naming chords by ear and sight becomes second nature.