How do you find the number of an interval?

Count the letter names from the lower note to the upper note, counting the lower note as 1. C to G is C, D, E, F, G: five letters, a 5th. Sharps and flats don’t change the number.

What are the interval qualities?

Perfect (P), Major (M), minor (m), Augmented (A) and diminished (d). Unisons, 4ths, 5ths and octaves can be Perfect; 2nds, 3rds, 6ths and 7ths can be Major or minor; any interval can be Augmented or diminished.

What is the difference between a major and a minor interval?

A minor interval is one semitone smaller than a Major interval, with the same letters. C to E is a Major 3rd (four semitones); C to E♭ is a minor 3rd (three semitones).

Why are 4ths and 5ths called perfect?

Above the tonic of a major scale, the unison, 4th, 5th and octave are called Perfect, and they are never Major or minor. Made a semitone larger they become Augmented; a semitone smaller, diminished.

How many semitones are in each interval?

Minor 2nd 1, Major 2nd 2, minor 3rd 3, Major 3rd 4, Perfect 4th 5, Augmented 4th or diminished 5th 6, Perfect 5th 7, minor 6th 8, Major 6th 9, minor 7th 10, Major 7th 11, octave 12.

An interval of six semitones, three whole tones. Spelled across four letters (F to B) it is an Augmented 4th; across five letters (B to F) it is a diminished 5th.

How do you invert an interval?

Move the lower note up an octave. The numbers add up to 9 (a 3rd becomes a 6th) and the quality swaps: Major becomes minor, Augmented becomes diminished, and Perfect stays Perfect.

Intervals

An interval is the distance between two notes. Its name has two parts. The number comes from counting letter names from the lower note to the upper one, counting both. The quality (Perfect, Major, minor, Augmented or diminished) comes from comparing the upper note with the lower note’s major scale. C up to E is a Major 3rd.

By Dan Vrancic, music theory teacher · Reviewed October 2026

What is an interval?

An interval is the distance between two notes. Two notes played one after the other make a melodic interval, written side by side. Two notes played together make a harmonic interval, written one above the other. Either way, C up to G is the same distance.

One after the other

Melodic

C, then G.

Together

Harmonic

C and G at once, stacked.

Every interval name has two parts: a number, such as 3rd or 5th, and a quality, such as Major or Perfect. Find the number first.

Step 1: count the letters for the number

Call the lower note 1 and count every letter name, every line and space, up to the upper note. C up to A passes through C, D, E, F, G and A, so it is a 6th.

C is 1. Count every line and space up to A: six letter names, a 6th.

Two notes on the same line or space are a unison (1). The same letter eight letter names higher is an octave (8).

Step 2: think in the lower note's major key

Measure from the tonic of a major scale to each of its notes and you get the diatonic intervals. The unison, 4th, 5th and octave are Perfect. The 2nd, 3rd, 6th and 7th are Major.

From C to every note of C major: P1 M2 M3 P4, then P5 M6 M7 P8.

The same names work above any note. Treat the lower note as a tonic and picture its major scale: if the upper note is in that scale, the interval is Perfect or Major. E major has G♯ as its 3rd, so E up to G♯ is a Major 3rd.

The five interval qualities

Move the upper note by a semitone, keeping its letter, and the number stays the same while the quality changes.

Quality	Short name	Used for	Size
Perfect	P	1, 4, 5, 8	In the lower note's major scale
Major	M	2, 3, 6, 7	In the lower note's major scale
minor	m	2, 3, 6, 7	One semitone smaller than Major
Augmented	A	any number	One semitone larger than Perfect or Major
diminished	d	any number	One semitone smaller than Perfect or minor

Perfect, Major and Augmented take a capital letter (P, M, A); minor and diminished take a lowercase one (m, d). That way M3 and m3 never get mixed up.

1, 4, 5, 8

The Perfect family: diminished, Perfect, Augmented

A 4th, 5th, unison or octave is never Major or minor.

2, 3, 6, 7

The Major family: diminished, minor, Major, Augmented

E♭♭ (a double flat) is played on the D key but written on E, so the interval is still a 3rd.

Intervals and semitones

Counting semitones tells you the size of an interval, but not its name. Every common interval above C:

Interval	Short name	Semitones	Above C
Perfect unison	P1	0	C
minor 2nd	m2	1	D♭
Major 2nd	M2	2	D
minor 3rd	m3	3	E♭
Major 3rd	M3	4	E
Perfect 4th	P4	5	F
Augmented 4th	A4	6	F♯
diminished 5th	d5	6	G♭
Perfect 5th	P5	7	G
minor 6th	m6	8	A♭
Major 6th	M6	9	A
minor 7th	m7	10	B♭
Major 7th	M7	11	B
Perfect octave	P8	12	C

How to name any interval

Count the letters
Lower note = 1. The count is the number.
Think in the lower note's major key
Find the note on the same letter in that major scale. That note makes the Perfect or Major interval.
Compare
Is the upper note the same, a semitone higher or a semitone lower? Move up or down the quality ladder one step per semitone.

A major has C♯, so A to C is a minor 3rd. F♯ major has C♯, so F♯ to C is a diminished 5th.

When a melody goes down, the lower note sounds second, but it is still the note you think from. Always name an interval from the bottom.

Inverting intervals

To invert an interval, move the lower note up an octave. The two numbers always add up to 9, and the quality swaps: Major ↔ minor, Augmented ↔ diminished, and Perfect stays Perfect.

Major ↔ minor

C–E inverts to E–C

Major 3rd → minor 6th.

Perfect stays Perfect

D–A inverts to A–D

Perfect 5th → Perfect 4th.

Try it: name the interval

Interval 1 of 6

C up to E♭: what is the number?

See it step by step

The interactive explainer from Lesson 15, with sound. Step through it at your own pace.

See it take shape · Interactive story

Same number, new quality

Keep the lower note where it is and move the upper note by a semitone. The letters, and so the number, stay the same; the size and the quality name change.

Step 1 of 12

G to B: Major 3rd, 4 semitones. Tap any key to hear it.

Start from Major

G to B is a Major 3rd

The lower note is the tonic. B is the 3rd note of G major, so G up to B is a Major 3rd: three letter names, four semitones.

Measure from the lower note, in its major key.

Use the arrow keys while a story control is focused.

Read the story as text

G to B is a Major 3rd
The lower note is the tonic. B is the 3rd note of G major, so G up to B is a Major 3rd: three letter names, four semitones.
One semitone smaller: minor
Lower the B to B♭. The notehead keeps its line, so the letters are still G and B and it is still a 3rd. It is one semitone smaller, so the Major 3rd becomes a minor 3rd.
Every Major interval has a minor partner
The 2nd, 3rd, 6th and 7th above G are Major in G major. Lower each top note a semitone and you get a minor 2nd, 3rd, 6th and 7th.
Think in the key of the lower note
A to C: A major has C♯ as its 3rd, and C is a semitone lower, so it is a minor 3rd. E to D: E major has D♯ as its 7th, so E to D is a minor 7th.
The lower note is still the tonic
When a melody falls from C to E, E is the lower note, so think in E major: its 6th is C♯ and C is a semitone lower, a minor 6th. Name it from the bottom whichever note sounds first.
One semitone larger: Augmented
C to G is a Perfect 5th. Raise the G to G♯ and the interval grows by a semitone while keeping its letters: an Augmented 5th.
Perfect never becomes minor
Lower the G to G♭ instead and the Perfect 5th shrinks to a diminished 5th. Unisons, 4ths, 5ths and octaves have no Major or minor: they go straight from Perfect to diminished.
The Major family has four rungs
C to E is a Major 3rd. E♯ makes it Augmented, E♭ minor, and E♭♭ diminished: the double flat lowers E two semitones, so it is played on D but is still a 3rd.
Same six semitones, different names
F to B: F major has B♭, and B is a semitone higher, so it is an Augmented 4th. B to F: B major has F♯, and F is a semitone lower, so it is a diminished 5th.
Ian the Interval Train
Write 1 to 8 with their home qualities, P M M P P M M P. Add A above every column, m below each M, and d below every P and every m. Tap any carriage to hear it from C.
Name it in three moves
Count the letters for the number. Think in the major key of the lower note to find the Perfect or Major interval. Then compare the top note with it and move along the ladder.
Name it, then write it
Name each interval: the number first, then the quality. Then write intervals above a given note: pick the letter, then the accidental.

Practice on paper

Free printable worksheets on this topic, each with an answer key.

Interval worksheets with answer keys

Questions about intervals

How do you find the number of an interval?: Count the letter names from the lower note to the upper note, counting the lower note as 1. C to G is C, D, E, F, G: five letters, a 5th. Sharps and flats don’t change the number.
What are the interval qualities?: Perfect (P), Major (M), minor (m), Augmented (A) and diminished (d). Unisons, 4ths, 5ths and octaves can be Perfect; 2nds, 3rds, 6ths and 7ths can be Major or minor; any interval can be Augmented or diminished.
What is the difference between a major and a minor interval?: A minor interval is one semitone smaller than a Major interval, with the same letters. C to E is a Major 3rd (four semitones); C to E♭ is a minor 3rd (three semitones).
Why are 4ths and 5ths called perfect?: Above the tonic of a major scale, the unison, 4th, 5th and octave are called Perfect, and they are never Major or minor. Made a semitone larger they become Augmented; a semitone smaller, diminished.
How many semitones are in each interval?: Minor 2nd 1, Major 2nd 2, minor 3rd 3, Major 3rd 4, Perfect 4th 5, Augmented 4th or diminished 5th 6, Perfect 5th 7, minor 6th 8, Major 6th 9, minor 7th 10, Major 7th 11, octave 12.
What is a tritone?: An interval of six semitones, three whole tones. Spelled across four letters (F to B) it is an Augmented 4th; across five letters (B to F) it is a diminished 5th.
How do you invert an interval?: Move the lower note up an octave. The numbers add up to 9 (a 3rd becomes a 6th) and the quality swaps: Major becomes minor, Augmented becomes diminished, and Perfect stays Perfect.

Members get · Practice arena

Race Melo in Intervals

60-second sprints against Melo at the level you pick, or against your own best run.

Talk it through with Melo. Ask Melo anything about intervals, have it quiz you, or work through a problem together step by step.

See all features See plans

In the course: Lesson 14: Diatonic Intervals, Lesson 15: Minor, Augmented & Diminished Intervals, Lesson 16: Interval Inversions

What is an interval?

Melodic

Harmonic

Step 1: count the letters for the number

Step 2: think in the lower note's major key

The five interval qualities

The Perfect family: diminished, Perfect, Augmented

The Major family: diminished, minor, Major, Augmented

Intervals and semitones

How to name any interval

Inverting intervals

C–E inverts to E–C

D–A inverts to A–D

Try it: name the interval

See it step by step

Same number, new quality

G to B is a Major 3rd

G to B is a Major 3rd

One semitone smaller: minor

Every Major interval has a minor partner

Think in the key of the lower note

The lower note is still the tonic

One semitone larger: Augmented

Perfect never becomes minor

The Major family has four rungs

Same six semitones, different names

Ian the Interval Train

Name it in three moves

Name it, then write it

Practice on paper

Questions about intervals

Race Melo in Intervals

Same number, new quality

G to B is a Major 3rd

G to B is a Major 3rd

One semitone smaller: minor

Every Major interval has a minor partner

Think in the key of the lower note

The lower note is still the tonic

One semitone larger: Augmented

Perfect never becomes minor

The Major family has four rungs

Same six semitones, different names

Ian the Interval Train

Name it in three moves

Name it, then write it