Understand how we measure the distance between notes, name intervals correctly and recognise them on the guitar.
What Is an Interval?
An interval is the distance in pitch between two notes. Intervals help us describe the relationships that make up melodies, scales, riffs and chords.
If the notes are played one after the other, the interval is melodic. If they sound together, the interval is harmonic. Either way, we use the same naming system.
How We Name an Interval
An interval name has two parts: a quality and a number.
Quality
+
Number
=
Interval Name
Choose a quality and number below to see how they combine to form an interval name. Please bear in mind that some combinations are intentionally restricted.
Quality
+
Number
=
Minor 3rdInterval name
Quality describes the type of interval (for example, major, minor or perfect). Number tells us how many note letters are included, counting both notes.
A First Example: C to E
C to E is a major 3rd. The number comes from counting the letter names: C (1), D (2), E (3). That gives us a 3rd.
The quality tells us which type of 3rd it is. C to E is major; C to E♭ is minor. Both cover the letters C, D and E, but their exact pitch distances differ.
Major 3rdC → E4 semitones
Minor 3rdC → E♭3 semitones
Measuring the Distance in Semitones
We can also measure an interval by counting semitones. On a standard fretted guitar, moving one fret along the same string changes the pitch by one semitone. In the tuning system used by modern guitars, an octave contains twelve semitones.
Starting on C, count each semitone until you reach E:
C1C♯2D3D♯4E
That is four semitones. C to E is therefore a major 3rd: the letters establish the number, while the precise semitone distance determines the quality for that spelling.
Compare it with C to E♭: that is only three semitones, so it is a minor 3rd.
Why This Matters on Guitar
Intervals give you a reusable way to understand guitar patterns. Instead of memorising isolated shapes, you can recognise a major 3rd, perfect 5th or minor 7th as a relationship between notes. That same relationship can be moved to a different starting note.
For example, a C major chord contains C, E and G: a major 3rd and a perfect 5th above C. Recognising those intervals helps explain why the notes belong together.
Counting Interval Numbers
For the number, count the musical letters from the first note to the second, including both endpoints. The note names matter here—not the number of frets or semitones.
Notes
Letter count
Number
C → D
C, D
2nd
C → E
C, D, E
3rd
C → F
C, D, E, F
4th
C → G
C, D, E, F, G
5th
Sharps and flats do not change the letter count. C to D♭ remains a 2nd, and C to F♯ remains a 4th. The accidentals can change the quality, but not the number.
Within an octave, the usual numbers are unison (1st), 2nd, 3rd, 4th, 5th, 6th, 7th and octave (8th).
Measuring Intervals on One String
Two semitones make one whole tone, which is two frets on the same string. To see interval distances in practice, start on C at the 3rd fret of the A string and move upwards.
Cfret 3 · rootE♭fret 6 · minor 3rdEfret 7 · major 3rdFfret 8 · perfect 4thGfret 10 · perfect 5th
From C (A string, fret 3)
A-string fret
Distance
Interval
E♭
6
3 semitones
Minor 3rd
E
7
4 semitones
Major 3rd
F
8
5 semitones
Perfect 4th
G
10
7 semitones
Perfect 5th
Try it: Play C at the 3rd fret, then E♭ at the 6th. Move E♭ up one fret to E. You have changed a minor 3rd into a major 3rd while keeping the starting note C.
Understanding Interval Qualities
The interval number identifies the letter span. The quality distinguishes the exact size and spelling within that number. The two main families work differently:
2nds, 3rds, 6ths and 7ths
Major or minor
C–E: major 3rd · C–E♭: minor 3rd
Unison, 4ths, 5ths and octaves
Perfect
C–F: perfect 4th · C–G: perfect 5th
Major and Minor
For the same interval number, a minor interval is one semitone smaller than its major form. Major/minor qualities apply to 2nds, 3rds, 6ths and 7ths.
Number
Major
Semitones
Minor
Semitones
2nd
C → D
2
C → D♭
1
3rd
C → E
4
C → E♭
3
6th
C → A
9
C → A♭
8
7th
C → B
11
C → B♭
10
Notice that each major/minor pair keeps the same letter names. Only the accidental and semitone distance change.
Perfect Intervals
Unisons, 4ths, 5ths and octaves normally use the quality perfect rather than major or minor.
Interval
Example
Semitones
Perfect unison
C → C (same pitch)
0
Perfect 4th
C → F
5
Perfect 5th
C → G
7
Perfect octave
C → next higher C
12
You will see perfect 4ths and 5ths repeatedly in guitar tuning, power chords and chord construction.
Augmented and Diminished
Sometimes an interval is one semitone larger or smaller than its usual major, minor or perfect form. We then use the qualities augmented and diminished.
Augmented means one semitone larger than a major or perfect interval of the same number.
Diminished means one semitone smaller than a minor or perfect interval of the same number.
Note pair
Semitones
Interval name
Why?
C → F♯
6
Augmented 4th
One above perfect 4th
C → G♭
6
Diminished 5th
One below perfect 5th
C → G♯
8
Augmented 5th
One above perfect 5th
C → F♭
4
Diminished 4th
One below perfect 4th
Important distinction: A minor interval is not the same thing as a diminished interval. For example, C–E♭ is a minor 3rd (3 semitones), while C–E𝄫 is a diminished 3rd (2 semitones).
Why Identical Distances Can Have Different Names
Two intervals can have the same semitone distance but different names. This is called enharmonic equivalence: the pitches sound the same in standard guitar tuning, but the written note letters are different.
C → F♯ spans four letters (C, D, E, F), making it an augmented 4th. C → G♭ spans five letters (C, D, E, F, G), making it a diminished 5th. Both measure six semitones.
C → F♯
4 letters · augmented 4th
6 semitones
C → G♭
5 letters · diminished 5th
6 semitones
Similarly, C–E (major 3rd) and C–F♭ (diminished 4th) both sound four semitones apart. Their names differ because interval naming considers both spelling and distance.
This is why counting frets alone cannot always give an interval its complete name.
Interval Reference: From C
This reference shows one common spelling for each semitone distance within an octave. The six-semitone distance is shown with its two familiar spellings.
Note from C
Interval name
Scale-degree formula
Semitones
C
Perfect unison
1
0
D♭
Minor 2nd
♭2
1
D
Major 2nd
2
2
E♭
Minor 3rd
♭3
3
E
Major 3rd
3
4
F
Perfect 4th
4
5
F♯ / G♭
Augmented 4th / diminished 5th
♯4 / ♭5
6
G
Perfect 5th
5
7
A♭
Minor 6th
♭6
8
A
Major 6th
6
9
B♭
Minor 7th
♭7
10
B
Major 7th
7
11
C (higher)
Perfect octave
8
12
The formula column uses scale-degree shorthand common in guitar lessons. For example, ♭3 means a lowered 3rd above the root; it is not a substitute for the formal interval name in every musical context.
Quick Check
Try answering these without the reference table first.
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.
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.
