Intervals

An interval is the distance between two notes, counted including both ends: C up to E passes C, D, E, so it is a third. The number says how far; the word in front — major, minor, perfect — says which kind.

Always count both ends. C to D is a second, not a first, and C to C is a unison. That runs against the instinct to count the gaps rather than the letters, and it is the first place beginners get stuck.

C up to E: three letters, C D E, so a third — and four half steps, so a major third.
C up to G: five letters, so a perfect fifth.

The number alone is not enough, because two thirds can differ by a half step: C–E spans four half steps (major third), C–E♭ spans three (minor third). So each number takes a quality word. Seconds, thirds, sixths and sevenths come in major and minor; unisons, fourths, fifths and octaves are called perfect, because they have no major or minor form.

IntervalHalf stepsFrom C
Minor 2nd1C–D♭
Major 2nd2C–D
Minor 3rd3C–E♭
Major 3rd4C–E
Perfect 4th5C–F
Perfect 5th7C–G
Major 6th9C–A
Perfect octave12C–C

How do you invert an interval?

To invert an interval, move its lower note up an octave (or its upper note down one). The two numbers always add up to 9, so a third becomes a sixth, a second a seventh and a fourth a fifth. The quality flips: major becomes minor, minor becomes major, augmented becomes diminished and diminished becomes augmented. Perfect stays perfect.

E up to C: a minor sixth, the major third C–E turned upside down.
IntervalInverts toExample
Major 2ndMinor 7thC–D → D–C
Minor 3rdMajor 6thC–E♭ → E♭–C
Major 3rdMinor 6thC–E → E–C
Perfect 4thPerfect 5thC–F → F–C
Augmented 4thDiminished 5thC–F♯ → F♯–C

What is a compound interval?

An interval wider than an octave is a compound interval. It is named by counting on: a ninth is an octave plus a second, a tenth an octave plus a third, and so on. To find its quality, subtract 7 from the number and read the simple interval left over, so C up to the E in the next octave is a major tenth, an octave plus a major third. Chord symbols use these names for their extensions: the 9 in Cmaj9 is the D above the octave.

Common questions

What is an interval in music?

The distance between two notes, named by how many letter names it spans. C to G spans five of them, so it is a fifth.

How do you count an interval?

Count the starting note as 1 and every letter name up to the top note, ignoring sharps and flats. D up to A is D E F G A, so a fifth; the accidentals only decide the quality.

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

A major third is four half steps (C–E) and a minor third is three (C–E♭). The major third gives a brighter color and the minor a darker one, and that single half step separates major triads from minor ones.

How do you invert an interval?

Lift the bottom note an octave. The new interval is the one that completes the octave: a minor third turns into a major sixth, and a perfect fifth into a perfect fourth.