Octaves
The 5 octave shapes
Every note on the guitar has its octave in one of five fixed shapes. Once you know the shapes, you can find any note's octave anywhere on the neck without thinking.
6 → 4, +2 frets
Two strings up, two frets across.
Low E string up to D string. The canonical bass-octave shape — most-used between strings 6 and 4 or strings 5 and 3.
5 → 3, +2 frets
Two strings up, two frets across.
A string up to G string. Same recipe as the bass shape because the A–D–G strings are all tuned a 4th apart.
4 → 2, +3 frets
Two strings up, **three** frets across — the B-string offset.
D string up to B string. The B string is tuned a major 3rd (not a 4th) from G — so the shape gains an extra fret.
3 → 1, +3 frets
Two strings up, three frets across.
G string up to high e. Same +3 offset as the previous shape — once you cross the G→B boundary, everything shifts.
Same string, +12 frets
Same string, twelve frets up.
On any single string, the octave is always 12 frets up. The 12th fret double-dot inlay marks this universally.
The +3-fret shape (string 4→2 and 3→1) is the trickiest because of the B-string offset. Practise it twice as much as the others and the rest of the neck unlocks.
What an octave is
An octave is the same note name twelve semitones higher (or lower). A and A, C and C — same pitch class, double the frequency. Two notes an octave apart sound like "the same note" sung at different vocal ranges; they blend so closely that the ear hears them as a unified pitch.
On guitar, every note exists in two or three places within a 12-fret span. Octave shapes are the geometric patterns that connect those locations.
Why octaves matter
If you only know notes in one spot, you're locked to that spot. Knowing octave shapes means you can:
- Find any note anywhere — see A at fret 5 on the low E? Its octave is at fret 7 on the D string. Same note, instantly available higher.
- Build chord voicings on the fly — every chord tone (root, 3rd, 5th, 7th) has multiple homes via octave shapes.
- Solo across the whole neck — every lick has the same notes in five different positions; octave shapes are the bridges.
- Tune by ear — every fret-5 note matches the next open string up; that's an octave-related interval relationship.
The 5 octave shapes
| Shape | Recipe |
|---|---|
| String 6 → 4 | 2 strings up, 2 frets across |
| String 5 → 3 | 2 strings up, 2 frets across |
| String 4 → 2 | 2 strings up, 3 frets across — the B-string offset |
| String 3 → 1 | 2 strings up, 3 frets across |
| Same string | 12 frets up — the universal octave |
The visualizer above shows all five with their exact root → octave positions and a dashed line connecting the pair.
The B-string offset (why guitar is weird)
Five of the six strings are tuned in perfect 4ths apart (5 semitones). The exception is the G → B interval — that's a major 3rd (4 semitones). One semitone narrower than the rest.
This means every shape that crosses the G → B boundary gains one extra fret. The "2 strings up, 2 frets across" shape becomes "2 strings up, 3 frets across" once you straddle G→B. This single fact is why every shape on guitar has two versions: pre-B-string and post-B-string.
Internalising the +3 offset saves you from years of "why does this shape work over here but not over there?" frustration.
Anchor relationships
Octave shapes unlock these anchor relationships:
| Two notes that are octaves | Frets apart |
|---|---|
| Fret 5 of low E, Fret 7 of D | The classic bass octave |
| Fret 5 of A, Fret 7 of G | Mid-range jazz octave |
| Fret 5 of D, Fret 8 of B | +3 because of the B offset |
| Fret 5 of G, Fret 8 of high e | +3 again |
| Any open string, Fret 12 of same string | Single-string octave |
If you can recall these five reference pairs cold, you have a "mental ruler" for measuring distances anywhere on the neck.