What Is a Music Interval?

An interval is the distance in pitch between two notes, measured in semitones.

“C and G,” “A and A,” “E and F”: whenever you compare two notes, you’re describing an interval. Every chord is built from intervals, and every scale is a sequence of them. They’re about as foundational as music theory gets.

Hear it first

The word “distance” makes more sense once you’ve heard a couple of intervals at different sizes.

1. Open the Interval Calculator
2. Set Note 1 to C and Note 2 to D, then press Play in sequence
3. Change Note 2 to G and play again
4. Notice how C–D is a small step while C–G is a wide, open leap

The result card names each one (a major second, then a perfect fifth) and shows its semitone count. Pairing the sound with the number is the quickest way to make these labels stick.

Why Learn Intervals?

Knowing your intervals lets you:

• Understand chord construction: A major chord is root + major third + perfect fifth
• Read and write scales: A major scale is a specific pattern of whole and half steps
• Hear music more accurately: Instead of guessing notes, you think “that’s a minor seventh above the root”
• Transpose fluently: The interval relationships stay the same across all keys

What Is a Semitone?

A semitone (also called a half step) is the smallest interval in standard Western music — the distance between any two adjacent keys on a piano, including black keys.

C to C# = 1 semitone. C to D = 2 semitones (one whole step).

All 13 Intervals

Symbol	Name	Semitones	Example (from C)
P1	Perfect Unison	0	C → C
m2	Minor Second	1	C → Db
M2	Major Second	2	C → D
m3	Minor Third	3	C → Eb
M3	Major Third	4	C → E
P4	Perfect Fourth	5	C → F
A4/d5	Augmented Fourth (Tritone)	6	C → F#
P5	Perfect Fifth	7	C → G
m6	Minor Sixth	8	C → Ab
M6	Major Sixth	9	C → A
m7	Minor Seventh	10	C → Bb
M7	Major Seventh	11	C → B
P8	Perfect Octave	12	C → C (one octave up)

Interval Quality: Perfect, Major, Minor

Intervals use quality descriptors:

Perfect (P) — applies to unisons, fourths, fifths, and octaves. These are the most stable intervals, with the simplest frequency ratios.

Major (M) and Minor (m) — applies to 2nds, 3rds, 6ths, and 7ths. Major intervals are one semitone wider than minor. Major tends to sound brighter; minor tends to sound darker.

Augmented (A) and Diminished (d) — one semitone wider/narrower than perfect or major/minor. The tritone (A4/d5) is the most common example.

Consonance and Dissonance

Intervals are also categorized by how “stable” or “tense” they sound:

Perfect consonances: P1, P5, P8 — the most stable, pure-sounding intervals
Imperfect consonances: m3, M3, m6, M6 — stable but with more color
Dissonances: m2, M2, A4, m7, M7 — tense, unstable, want to resolve

These categories aren’t about “good” vs “bad” — dissonances are essential to musical motion and expression.

Intervals and Chords

The difference between a major and a minor chord is just one semitone — specifically, whether the third is major or minor.

Chord	Third
Major chord (bright)	Major third (4 semitones)
Minor chord (dark)	Minor third (3 semitones)

This single half-step difference is responsible for one of the most emotionally significant distinctions in music.

What to try next

Build one chord from intervals and listen to it appear. Set Note 1 to C and Note 2 to E (a major third), then move Note 2 to G (a perfect fifth); you’ve just spelled out a C major triad one interval at a time. Switch the third to Eb and the same chord turns minor. Hearing chords as stacked intervals is what makes the rest of harmony feel less like memorization.

→ Build and compare intervals in the Interval Calculator