What Is an Interval?
An interval is the distance between two notes. It tells us how far apart those notes are in pitch.
Intervals may be melodic, with the notes played successively, or harmonic, with the notes sounded together.
We describe an interval using two parts:
- Its number, such as a 2nd, 3rd or 5th
- Its quality, such as major, minor or perfect
For example, C to E is a major 3rd.
The number tells us that the interval spans three letter names:
C, D, E
The quality tells us the precise size of that 3rd.
Why Intervals Matter
Intervals are not just theory terms. They are the structure behind:
- Scale formulas
- Chord construction
- Melodic movement
- Harmonic tension and resolution
Once you understand intervals, you can break down musical ideas into patterns that can be recognised, repeated and moved into different keys.
Semitones and Whole Tones
In 12-tone equal temperament, an octave is divided into 12 equal steps. Each step is called a semitone.
On the guitar, moving by one fret changes the pitch by one semitone.
For example:
- Moving from fret 3 to fret 4 is one semitone.
- Moving from C to C♯ is one semitone.
- Moving from E to F is one semitone.
Two semitones make one whole tone. On the guitar, this means moving by two frets.
Semitones tell us an interval’s sounding distance. To name it correctly, we must also consider the letter names of the two notes.
What Is an Interval Number?
An interval number is found by counting the letter names from the starting note to the ending note.
Always include both the starting note and the ending note in the count.
Example
Letter Count
Result
C to E
C
→
1,
D
→
2,
E
→
3
3rd
C to F
C
→
1,
D
→
2,
E
→
3,
F
→
4
4th
Sharps and flats do not change the interval number because the number is based on letter names.
For example:
C to D♭ is still a 2nd because C to D = 2.
C to E♭ is still a 3rd because C to E = 3.
C to F♯ is still a 4th because C to F = 4.
Within one octave, interval numbers include:
Unison, 2nd, 3rd, 4th, 5th, 6th, 7th and octave
The number alone does not tell us the interval's exact size. For that, we also need its quality.
Interval Qualities
The interval number tells us how many letter names are included.
The interval quality tells us the interval's precise size in relation to that number.
Interval Number
Tells us how many letter names are involved.
Interval Quality
Tells us the interval's precise size in relation to that number.
C to E and C to E♭ are both 3rds because both span the letters C, D and E.
However, C to E is four semitones and is a major 3rd. C to E♭ is three semitones and is a minor 3rd.
The number remains the same, but the quality changes because the semitone distance is different.
The Main Interval Qualities
The main interval qualities are:
Major
Minor
Perfect
Augmented
Diminished
Major and Minor
Major and minor apply to:
2nds
3rds
6ths
7ths
A minor interval is one semitone smaller than the major interval with the same number.
C to D = 2 semitones
Major 2nd
C to D♭ = 1 semitone
Minor 2nd
C to E = 4 semitones
Major 3rd
C to E♭ = 3 semitones
Minor 3rd
C to A = 9 semitones
Major 6th
C to A♭ = 8 semitones
Minor 6th
C to B = 11 semitones
Major 7th
C to B♭ = 10 semitones
Minor 7th
In each pair, the letter count stays the same. Only the semitone distance changes.
A major interval lowered once becomes minor. A major interval lowered twice becomes diminished. A major interval raised once becomes augmented.
A minor interval raised by one semitone becomes major. A minor interval lowered by one semitone becomes diminished.
Perfect Intervals
Perfect applies to:
Unison
4ths
5ths
Octaves
These intervals do not have major and minor forms in their standard state.
C to C = 0 semitones
Perfect unison
C to F = 5 semitones
Perfect 4th
C to G = 7 semitones
Perfect 5th
C to C (next C up) = 12 semitones
Perfect octave
When a perfect interval is raised by one semitone, it becomes augmented.
When it is lowered by one semitone, it becomes diminished.
Augmented and Diminished Intervals
Augmented and diminished describe intervals that have been expanded or reduced beyond their major, minor or perfect forms.
For perfect intervals:
- Perfect raised by one semitone becomes augmented.
- Perfect lowered by one semitone becomes diminished.
For major and minor intervals:
- Major lowered once becomes minor.
- Major lowered twice becomes diminished.
- Major raised once becomes augmented.
Examples:
C to F♯ = 6 semitones
Augmented 4th
C to F♭ = 4 semitones
Diminished 4th
C to G♯ = 8 semitones
Augmented 5th
C to G♭ = 6 semitones
Diminished 5th
In scale and chord formulas, ♭ and ♯ indicate that a reference interval has been lowered or raised by one semitone. In formal interval names, we express the result using qualities such as minor, major, perfect, augmented and diminished.
Enharmonic Interval Spellings
Some intervals contain the same number of semitones and sound the same in equal temperament but have different names.
For example:
- C to E is a major 3rd.
- C to F♭ is a diminished 4th.
Both intervals contain four semitones, but they are not named the same way.
C to E spans three letter names: C, D, E.
C to F♭ spans four: C, D, E, F.
These are called enharmonically equivalent intervals. They sound the same on a modern guitar but are spelled differently because they have different letter counts and musical functions.
Another common example is:
- C to F♯: augmented 4th
- C to G♭: diminished 5th
Both contain six semitones, but one is a type of 4th and the other is a type of 5th.
Chromatic Intervals from C
The chromatic scale contains all 12 pitch positions within an octave.
The table below shows each semitone distance from C, its note spelling, formal interval name and scale-degree formula.
| Semitones | Note from C | Interval name | Scale-degree formula |
|---|
| 0 | C | Perfect unison | 1 |
|---|
| 1 | D♭ | Minor 2nd | ♭2 |
|---|
| 2 | D | Major 2nd | 2 |
|---|
| 3 | E♭ | Minor 3rd | ♭3 |
|---|
| 4 | E | Major 3rd | 3 |
|---|
| 5 | F | Perfect 4th | 4 |
|---|
| 6 | F♯ / G♭ | Augmented 4th / diminished 5th | ♯4 / ♭5 |
|---|
| 7 | G | Perfect 5th | 5 |
|---|
| 8 | A♭ | Minor 6th | ♭6 |
|---|
| 9 | A | Major 6th | 6 |
|---|
| 10 | B♭ | Minor 7th | ♭7 |
|---|
| 11 | B | Major 7th | 7 |
|---|
| 12 | C | Perfect octave | 8 |
|---|
This shows the twelve chromatic pitch distances available within one octave, using the interval names most commonly encountered in basic scale formulas.
Other spellings are possible depending on the musical context, but these are the forms you will encounter most often when working with scales, chords and guitar theory.
Frequently Asked Questions
What is an interval in music?
An interval is the distance between two notes. Its full name combines a number, determined by the note letters, with a quality such as major, minor or perfect.
How do intervals work on guitar?
Each fret represents one semitone. Moving two frets along the same string raises the pitch by two semitones. The interval’s correct name also depends on the letter names used to spell the two notes.
How do you count an interval number?
Count the letter names from the starting note to the ending note, including both notes. C to E is a 3rd because the count is C–D–E. Sharps and flats do not change the interval number.
What is the difference between major and minor intervals?
Major and minor qualities apply to 2nds, 3rds, 6ths and 7ths. A minor interval is one semitone smaller than the corresponding major interval.
Which intervals are called perfect?
Unisons, 4ths, 5ths and octaves belong to the perfect interval group. Raising a perfect interval by one semitone makes it augmented. Lowering it by one semitone makes it diminished.
What is a tritone?
A tritone spans six semitones. Depending on its spelling, it can be an augmented 4th, such as C to F♯, or a diminished 5th, such as C to G♭.
Why can two intervals sound the same but have different names?
In equal temperament, differently spelled intervals can share the same pitch distance. For example, C to F♯ is an augmented 4th, while C to G♭ is a diminished 5th. Both span six semitones, but their letter counts and musical functions differ.
What is the difference between melodic and harmonic intervals?
A melodic interval occurs when two notes are played successively. A harmonic interval occurs when the notes sound together.
Why should guitarists learn intervals?
Intervals provide the structure behind scales, chords, melodies and fretboard patterns. Recognising interval shapes makes musical ideas easier to transpose and apply in different keys.
See Intervals on the Guitar Fretboard
Once you understand how intervals are measured, try visualising them across the guitar neck. The Interactive Fretboard Tool lets you highlight notes and see interval relationships in different positions.
You can also see how these intervals combine to form chords using the Guitar Chord Finder.
