Intervals

An interval is the distance between two notes, measured both in semitones and in letter names. Both measurements are needed. Two notes six frets apart are a tritone whatever they are called, but whether that tritone is written as an augmented fourth or a diminished fifth decides how it is handled in the key it appears in.

The intervals within an octave

The semitone count is exact; the name is a convention that follows the letter names. The examples are all measured upwards from C.

Interval	Symbol	Semitones	Example	Frets on one string	Notes
Perfect unison	P1	0	C to C	0	The same pitch. Two parts a unison apart play the same note.
Minor second	m2	1	C to Db	1	The smallest step in equal temperament. On one string it is one fret; across two adjacent strings it is a large stretch.
Major second	M2	2	C to D	2	One whole tone: two frets on one string, or the interval between adjacent open strings except between G and B.
Minor third	m3	3	C to Eb	3	Three frets. The third of a minor triad, and one half of the octave division in a diminished seventh chord.
Major third	M3	4	C to E	4	Four frets. The third of a major triad, and the interval that separates the two lowest strings of a standard-tuned guitar by three of them.
Perfect fourth	P4	5	C to F	5	Five frets. The interval between all adjacent strings of a standard-tuned guitar except between the third and second, which are a major third apart.
Tritone	A4 / d5	6	C to F#	6	Six frets, exactly half an octave. Ambiguous in spelling and unstable in function; it is the interval between the third and seventh of a dominant seventh chord.
Perfect fifth	P5	7	C to G	7	Seven frets, or the same fret one string lower. The interval that defines both the power chord and the tuning of four of the six strings.
Minor sixth	m6	8	C to Ab	8	Eight frets. Inversion of the major third.
Major sixth	M6	9	C to A	9	Nine frets. Inversion of the minor third; the interval between the root and the sixth of a sixth chord.
Minor seventh	m7	10	C to Bb	10	Ten frets, or the same fret two strings lower. The seventh of a dominant seventh chord.
Major seventh	M7	11	C to B	11	Eleven frets, or one fret below the octave. The seventh of a major seventh chord.
Perfect octave	P8	12	C to C	12	Twelve frets. The same note name, doubling the frequency.
Minor ninth	m9	13	C to Db an octave above	1 + 12	An octave plus a minor second. A flat ninth is the most altered available upper extension of a dominant chord.
Major ninth	M9	14	C to D an octave above	2 + 12	An octave plus a major second. The ninth of a ninth chord.
Augmented ninth	A9	15	C to D# an octave above	3 + 12	An octave plus an augmented second, written #9. The chord tone that gives the 7#9 chord its bite.
Perfect eleventh	P11	17	C to F an octave above	5 + 12	An octave plus a perfect fourth. Normally omitted from a dominant chord because it clashes with the third.
Augmented eleventh	A11	18	C to F# an octave above	6 + 12	An octave plus an augmented fourth, written #11. Stable over a major seventh chord because it lies a tritone from the root.
Perfect twelfth	P12	19	C to G an octave above	7 + 12	An octave plus a perfect fifth. Three octaves are almost seven of them, which is why stacking fifths is not a practical way to divide the octave.
Minor thirteenth	m13	20	C to Ab an octave above	8 + 12	An octave plus a minor sixth, written b13. Used over altered dominant chords.
Major thirteenth	M13	21	C to A an octave above	9 + 12	An octave plus a major sixth. The top extension of a thirteenth chord.

Interval

Symbol

Semitones

Example

Frets on one string

Notes

Perfect unison

C to C

The same pitch. Two parts a unison apart play the same note.

Minor second

C to Db

The smallest step in equal temperament. On one string it is one fret; across two adjacent strings it is a large stretch.

Major second

C to D

One whole tone: two frets on one string, or the interval between adjacent open strings except between G and B.

Minor third

C to Eb

Three frets. The third of a minor triad, and one half of the octave division in a diminished seventh chord.

Major third

C to E

Four frets. The third of a major triad, and the interval that separates the two lowest strings of a standard-tuned guitar by three of them.

Perfect fourth

C to F

Five frets. The interval between all adjacent strings of a standard-tuned guitar except between the third and second, which are a major third apart.

Tritone

A4 / d5

C to F#

Six frets, exactly half an octave. Ambiguous in spelling and unstable in function; it is the interval between the third and seventh of a dominant seventh chord.

Perfect fifth

C to G

Seven frets, or the same fret one string lower. The interval that defines both the power chord and the tuning of four of the six strings.

Minor sixth

C to Ab

Eight frets. Inversion of the major third.

Major sixth

C to A

Nine frets. Inversion of the minor third; the interval between the root and the sixth of a sixth chord.

Minor seventh

C to Bb

Ten frets, or the same fret two strings lower. The seventh of a dominant seventh chord.

Major seventh

C to B

Eleven frets, or one fret below the octave. The seventh of a major seventh chord.

Perfect octave

C to C

Twelve frets. The same note name, doubling the frequency.

Minor ninth

C to Db an octave above

1 + 12

An octave plus a minor second. A flat ninth is the most altered available upper extension of a dominant chord.

Major ninth

C to D an octave above

2 + 12

An octave plus a major second. The ninth of a ninth chord.

Augmented ninth

C to D# an octave above

3 + 12

An octave plus an augmented second, written #9. The chord tone that gives the 7#9 chord its bite.

Perfect eleventh

P11

C to F an octave above

5 + 12

An octave plus a perfect fourth. Normally omitted from a dominant chord because it clashes with the third.

Augmented eleventh

A11

C to F# an octave above

6 + 12

An octave plus an augmented fourth, written #11. Stable over a major seventh chord because it lies a tritone from the root.

Perfect twelfth

P12

C to G an octave above

7 + 12

An octave plus a perfect fifth. Three octaves are almost seven of them, which is why stacking fifths is not a practical way to divide the octave.

Minor thirteenth

m13

C to Ab an octave above

8 + 12

An octave plus a minor sixth, written b13. Used over altered dominant chords.

Major thirteenth

M13

C to A an octave above

9 + 12

An octave plus a major sixth. The top extension of a thirteenth chord.

Every interval above every root

Spelled note names for each interval above each of the twelve roots. Spelling follows the letter names of the key, so the interval above C# is written E# rather than F, because the third degree of C# major is E something. Where a spelling is awkward, the enharmonic equivalent is a semitone away with a different letter.

Root	m2	M2	m3	M3	P4	A4	P5	m6	M6	m7	M7	Octave
C	Db	D	Eb	E	F	F#	G	Ab	A	Bb	B	C
C#	D	D#	E	E#	F#	F##	G#	A	A#	B	B#	C#
D	Eb	E	F	F#	G	G#	A	Bb	B	C	C#	D
Eb	Fb	F	Gb	G	Ab	A	Bb	Cb	C	Db	D	Eb
E	F	F#	G	G#	A	A#	B	C	C#	D	D#	E
F	Gb	G	Ab	A	Bb	B	C	Db	D	Eb	E	F
F#	G	G#	A	A#	B	B#	C#	D	D#	E	E#	F#
G	Ab	A	Bb	B	C	C#	D	Eb	E	F	F#	G
Ab	Bbb	Bb	Cb	C	Db	D	Eb	Fb	F	Gb	G	Ab
A	Bb	B	C	C#	D	D#	E	F	F#	G	G#	A
Bb	Cb	C	Db	D	Eb	E	F	Gb	G	Ab	A	Bb
B	C	C#	D	D#	E	E#	F#	G	G#	A	A#	B

Root

Octave

F##

Bbb

Intervals and the guitar

The guitar is tuned in fourths except between the third and second strings, which are a major third apart. That single irregularity is why scale and chord shapes shift by one fret when they cross between those two strings, and why barre chords on the fifth and sixth strings have the same shape but not the same fingering.

String pair	Interval between open strings	Semitones up	Upward	Semitones down	Downward	Fret offset
6th to 5th	perfect fourth	5	Perfect fourth	7	Perfect fifth	5
5th to 4th	perfect fourth	5	Perfect fourth	7	Perfect fifth	5
4th to 3rd	perfect fourth	5	Perfect fourth	7	Perfect fifth	5
3rd to 2nd	major third	4	Major third	8	Minor sixth	4
2nd to 1st	perfect fourth	5	Perfect fourth	7	Perfect fifth	5

Reading intervals off the fretboard

On one string, an interval of N semitones is N frets.
Two notes on adjacent strings at the same fret are a perfect fourth apart, except across the third and second strings, where they are a major third apart.
A perfect fifth is the same fret on the string below, except across the third and second strings, where it is one fret lower.
A major third is one fret lower on the next string down, except across the third and second strings, where it is on the same fret.
An octave is two strings and two frets up, except across the third and second strings, where it is three frets up. The same shapes return unchanged after the twelfth fret.

The fret offsets above follow standard tuning, E A D G B E. In any altered tuning the offsets change; see Tunings.

ReferenceCircle of fifths12 keys, relative minors, order of accidentals
ReferenceKey signatures15 major keys, 15 minor keys
ReferenceNashville number systemdegrees 1-7 in all 12 keys
CapoCapo chart12 capo positions × 24 target keys
HubScales and modes12 roots × 20 scales
HubChords12 roots × 23 qualities
HubFretboard maps12 note maps, 12 degree maps
HubReferencefour reference pages

Section: Reference · Theory Atlas