Every chord is built from a specific formula — a root note plus a series of intervals. Once you understand the formula, you can construct any chord in any key. The formula is the blueprint; the fretboard is where you build it.
A chord formula tells you exactly which notes to stack on top of a root. For example, the major chord formula is: root + major third (4 semitones) + perfect fifth (7 semitones). If you apply this formula to C, you get C + E + G. Apply it to G, you get G + B + D. The intervals stay constant; only the starting pitch changes.
This is why understanding chord construction through intervals is so powerful. Instead of memorizing hundreds of chord shapes, you memorize a handful of formulas. Then you apply those formulas anywhere on the fretboard. A single formula creates infinite chord possibilities.
When building major chords, the formula is always the same: root + 4 semitones + 7 semitones. This consistency is what makes chords predictable and understandable. Different chord types have different formulas, but within each type, the intervals never change.
The Major Chord: The Foundation of All Chords
The major chord is the simplest extended chord structure. Formula: root + major third (4 semitones) + perfect fifth (7 semitones).
Let’s build a C major chord using this formula:
- Start with C (root)
- Go up 4 semitones: C → C# (1) → D (2) → D# (3) → E (4). That’s E.
- Go up 7 semitones from C: C → C# (1) → D (2) → D# (3) → E (4) → F (5) → F# (6) → G (7). That’s G.
- Result: C, E, G (a C major chord)
On the guitar, these intervals translate to fret positions. If C is on the third fret of the A string, E is on the second fret of the G string (7 frets lower but same note in a different octave), and G is on the open low E string. Different positions, but the same note names create the same chord.
The major chord is the harmonic foundation. All other chords are variations or extensions of it. Understanding how to build major chords gives you the starting point for understanding all chord construction.
Building Minor Chords: The One-Semitone Difference
The minor chord formula differs from major by just one semitone in the third. Formula: root + minor third (3 semitones) + perfect fifth (7 semitones).
Building A minor using this formula:
- Start with A (root)
- Go up 3 semitones: A → A# (1) → B (2) → C (3). That’s C.
- Go up 7 semitones from A: A → A# (1) → B (2) → C (3) → C# (4) → D (5) → D# (6) → E (7). That’s E.
- Result: A, C, E (an A minor chord)
Compare A major (A, C#, E) to A minor (A, C, E). The only difference is C natural instead of C#. One semitone. Yet that single semitone changes the entire character from major (bright) to minor (dark). This shows how precisely interval construction determines chord character.
Understanding minor chord construction is essential because minor chords are equally fundamental to major chords in music. Most songs use both major and minor chords, and the construction process is identical — only the intervals differ.
Seventh Chords: Adding Color and Complexity
Seventh chords extend beyond the basic triad by adding one more interval: the seventh. Different seventh chords use different seventh intervals, creating distinct characters.
Major 7th: root + major third (4) + perfect fifth (7) + major seventh (11 semitones)
Dominant 7th: root + major third (4) + perfect fifth (7) + minor seventh (10 semitones)
Minor 7th: root + minor third (3) + perfect fifth (7) + minor seventh (10 semitones)
Building a Cmaj7:
- C (root), E (4 semitones), G (7 semitones), B (11 semitones)
- Result: a bright, open, sophisticated chord
Building a C7 (dominant):
- C (root), E (4 semitones), G (7 semitones), Bb (10 semitones)
- Result: a bluesy, tense chord
Building a Cm7:
- C (root), Eb (3 semitones), G (7 semitones), Bb (10 semitones)
- Result: a dark, jazzy chord
Same root and fifth, but different third and seventh quality create dramatically different sounds. Understanding seventh chord construction and formulas opens the door to sophisticated harmony.
Extended Chords: Going Beyond Sevenths
Extended chords add even more intervals: ninths, elevenths, and thirteenths. Each extension adds harmonic richness and sophistication.
9th chord (Cmaj9): root + major third + perfect fifth + major seventh + major ninth (14 semitones)
11th chord (Cmaj11): add perfect eleventh (17 semitones) to the 9th
13th chord (Cmaj13): add major thirteenth (21 semitones) to the 11th
Building a Cmaj9:
- C, E, G, B (so far, this is Cmaj7)
- Add D (14 semitones from C)
- Result: C, E, G, B, D (a complex, jazz-influenced chord)
Extended chords require strategic voicing on guitar because there are so many notes. You often omit certain notes (usually the third or fifth) to keep the chord playable while maintaining its identity through the seventh and the extension.
Suspended Chords: Replacing the Third
Sus chords replace the major or minor third with either a second (sus2) or a fourth (sus4). This creates an open, unresolved quality.
Sus2: root + major second (2 semitones) + perfect fifth (7 semitones)
Sus4: root + perfect fourth (5 semitones) + perfect fifth (7 semitones)
Building Csus2:
- C (root), D (2 semitones), G (7 semitones)
- Result: C, D, G (an open, floating chord with no third)
Building Csus4:
- C (root), F (5 semitones), G (7 semitones)
- Result: C, F, G (a classical, hanging chord with no third)
Sus chords are useful because they’re neither major nor minor, allowing them to fit into progressions before resolving to a major or minor chord. Understanding sus chord formulas shows how removing the third creates harmonic ambiguity that can be very useful.
Translating Formulas to Fretboard Positions
Once you know a chord formula (intervals in semitones), translating it to the fretboard is straightforward: find the root note, then move the specified number of semitones to find each chord tone.
For a Cmaj7 chord:
- Find C on a string (say, open low E string)
- Move 4 semitones up on the same string or find E on another string
- Move 7 semitones up from C
- Move 11 semitones up from C
- Play those notes in whatever octaves work for your voicing
The same chord can be voiced in dozens of ways because those same four note names can appear in any octave or order on the fretboard. The voicing changes the sound, but the note names stay constant.
Understanding guitar chord construction through intervals makes you able to build chords anywhere. A major third (4 semitones) is always 4 frets on the same string, or equivalent intervals on different strings. A perfect fifth (7 semitones) is always 7 frets on the same string, or the corresponding interval on other strings.
Common Chord Formulas at a Glance
Major: root + 4 + 7
Minor: root + 3 + 7
Augmented: root + 4 + 8
Diminished: root + 3 + 6
Maj7: root + 4 + 7 + 11
m7: root + 3 + 7 + 10
Dom7: root + 4 + 7 + 10
Sus2: root + 2 + 7
Sus4: root + 5 + 7
Add9: root + 4 + 7 + 14
Power: root + 7 (no third)
Memorizing these formulas is more efficient than memorizing shapes. With formulas, you can construct any chord in any position on the fretboard.
Frequently Asked Questions
Why is learning formulas better than memorizing shapes?
Formulas are universal and portable. One formula (root + 4 + 7 for major) creates major chords in every key and every position. Memorizing shapes limits you to specific positions and requires relearning for each key.
Can I use the same formula for different chord types?
No. Each chord type has its own formula. Major and minor differ in the third (4 vs. 3 semitones). Dominant 7th and major 7th differ in the seventh (10 vs. 11 semitones). The formulas determine the chord type.
What if I want to play a chord in an unusual voicing?
As long as it contains the correct note names (determined by the formula), it’s the same chord. A Cmaj7 played as G-B-E-C is still a Cmaj7 because it contains those four note names. The voicing is different, but the chord identity is the same.
How do I know which notes to include if a chord has many notes?
For guitar, you often omit notes strategically to keep the chord playable. For extended chords (9th, 11th, 13th), include the root, the seventh (for color), and the extension. The fifth and third can often be omitted.
Does the order of notes matter when I’m constructing a chord?
The chord name is determined by which notes are present, not their order. But the voicing (order and octave placement) affects how the chord sounds. C-E-G sounds different from G-C-E even though they’re both C major chords.
Can I construct a chord I’ve never heard before by using a formula?
Absolutely. If you know the formula, you can build any chord. Not all combinations will sound “good” to your ear, but they’re all technically valid chords. Exploration through formula construction can lead to discovering new voicings or chord colors.