A chord is built by stacking every other note from a scale. Take the 1st, 3rd, and 5th notes of a major scale and you get a major chord. Lower the 3rd by one fret (a half step) and you get a minor chord.
That’s the whole secret. Every chord you’ve ever played — every open shape, every barre chord, every weird jazz voicing someone showed you at a jam night — comes back to this one idea.
The 1-3-5 Formula
Here’s how it works. Take any major scale. Number the notes 1 through 7. Now pick out the 1st, 3rd, and 5th.
Those three notes are your major chord. That’s it.
Let’s use C major because there are no sharps or flats to worry about. The C major scale is:
C – D – E – F – G – A – B
Number them:
| 1 | 2 | 3 | 4 | 5 | 6 | 7 |
|---|---|---|---|---|---|---|
| C | D | E | F | G | A | B |
Grab the 1st, 3rd, and 5th: C – E – G.
That’s a C major chord. Three notes.
Look at the open C chord you already know. Every note in that shape is either a C, an E, or a G. Some are doubled at different octaves, but the building blocks are those same three notes.
Now let’s do G major. The G major scale is G – A – B – C – D – E – F#. Grab the 1, 3, and 5: G – B – D.
Same idea. The open G chord is just those three notes arranged across six strings. Nothing more.
What Makes a Chord Minor
This is where it gets really good.
A minor chord uses the same formula — 1, 3, 5 — but the 3rd gets lowered by one fret. One half step. That’s the only difference between major and minor.
I used to think major and minor were completely different animals. But they’re not — they’re separated by a single fret. One tiny move.
We write it as 1 – b3 – 5 (the “b” means flat, which just means “lowered by a half step”).
Back to our C chord. A C major chord is C – E – G. To make it C minor, lower the E by one half step. E goes down to Eb.
C minor = C – Eb – G = 1 – b3 – 5
One note changed. That’s all it takes to go from bright and happy to dark and moody. The 3rd is the note that controls whether a chord sounds major or minor — it’s the most important note in the chord after the root.
This is true for every major/minor pair. A and Am? Same root and 5th — the only difference is the 3rd. D and Dm? Same thing. Always.
7th Chords: Adding One More Note
So if a basic chord is 1-3-5… what happens when you keep stacking and add the 7th note from the scale?
You get a 7th chord. Four notes instead of three.
There are two main types you’ll run into, and the difference matters more than you’d expect.
Dominant 7th (like G7)
A dominant 7th chord takes your major chord (1-3-5) and adds a flatted 7th — the 7th note of the scale lowered by a half step.
G major scale: G – A – B – C – D – E – F#
G major chord: G – B – D (1-3-5)
Now add the flatted 7th. F# lowered by a half step = F natural.
G7 = G – B – D – F = 1 – 3 – 5 – b7
Compare that to a regular G chord — the only difference is one note on the 1st string. But the sound… G7 has that bluesy, unresolved pull. It wants to go somewhere. It’s the chord that creates tension before a resolution (and it’s half the reason blues music sounds the way it does).
Major 7th (like Cmaj7)
A major 7th chord keeps the 7th as-is — no flattening. It’s the natural 7th straight from the scale.
C major scale: C – D – E – F – G – A – B
Cmaj7 = C – E – G – B = 1 – 3 – 5 – 7
That B note (the natural 7th) gives the chord a smooth, dreamy quality. Cmaj7 sounds lush, open, almost jazzy. Very different vibe from a dominant 7th.
Quick rule: when you see just a “7” after a chord name (like G7), it means dominant — flatted 7th, tense sound. When you see “maj7” (like Cmaj7), that’s the natural 7th — warm and pretty. The naming felt confusing to me at first, but once you hear the difference, it sticks.
Why This Matters for Guitarists
You might be thinking — okay, but I already know how to play C and G. Why do I need to know how they’re built?
Fair question. Here’s why it’s worth the effort:
You can build chords anywhere on the neck. Once you know a chord is just three notes, you can find those notes in different spots and create your own shapes. That’s how players come up with voicings you won’t find in any chord book.
You can understand why shapes are the way they are. Ever wonder why the C shape and the A shape look so different even though they’re both major chords? Different root notes mean the 1, 3, and 5 land on different frets and strings.
Transposing gets easy. The formula works in any key, so you can build any major chord from scratch — even in keys where you don’t know the shapes yet.
You can modify chords on the fly. Want minor? Drop the 3rd by one fret. Want a 7th? Find the flatted 7th and add it in. Instead of memorizing hundreds of separate shapes, you’re working from one system. The good news is that one system covers pretty much everything.
Once you see this… the fretboard stops feeling like a maze of random shapes. It starts to feel like a grid with logic to it. This connects directly to understanding what chords go together and how major and minor keys work. It’s all the same system underneath.
Watch: How to Create Your Own Guitar Chords
This shows how to use these building blocks to create your own chord voicings anywhere on the neck:
FAQ
Do I need to know the major scale to build chords? It helps a lot. The major scale gives you the numbered notes (1 through 7) that chord formulas are based on. If you know the major scale, chord formulas click into place fast.
What about sus chords and add9 chords? Same principle, different notes. A sus4 replaces the 3rd with the 4th (1-4-5). A sus2 replaces it with the 2nd (1-2-5). An add9 is 1-3-5 plus the 9th (which is really just the 2nd up an octave). Once you know 1-3-5, these are all small tweaks from there.
Is a minor 7th chord different from a dominant 7th? Yes. A dominant 7th has a major 3rd and a flatted 7th (1-3-5-b7). A minor 7th has a minor 3rd and a flatted 7th (1-b3-5-b7). So Am7, for example, is A-C-E-G. The “minor” part comes from the b3, and the “7” part comes from the b7.
Can I build chords from scales other than the major scale? You can, but the major scale is the standard reference point. When people say “flat the 3rd,” they mean flat it compared to the major scale. Even with exotic jazz chords, the major scale is still the measuring stick.
Why do some chord shapes use more than three notes if chords only have three? Guitar has six strings, but a basic chord only has three different notes. Those notes get repeated at different octaves. A G chord shape has six notes ringing, but they’re all G, B, or D — just doubled up.
Go Deeper
Understanding how chords are built is one of the biggest “aha” moments in guitar theory — once you see this, everything else clicks a little faster. If you want to see how this connects to keys, progressions, and the stuff you’re actually playing, grab the free Crash Course in Guitar Theory. It ties chord formulas to the five most common guitar keys.