Pitch & Intervals

Major Third

Written as M3

Definition

A major third (M3) is an interval of four half steps spanning three letter names, such as C–E, F–A or D–F♯. It is the bottom interval of a major chord and sounds bright and stable.

A major third spans three letter names and four half steps: C up to E, F up to A, G up to B, D up to F♯. Abbreviated M3, it measures 400 cents in equal temperament.

Three one-bar examples of three half notes each: the lower note, the upper note, then both together. C4 and E4, F4 and A4 in treble clef; D3 and F sharp 3 in bass clef. — Three major thirds, each shown in one bar: the lower note, the upper note, then both together. C–E and F–A in the treble clef, D–F♯ in the bass clef.

Counting it

C–D–E is three letters, so C–E is a 3rd. Count the half steps from C: C♯ (1), D (2), D♯ (3), E (4). Four half steps make it major; three would make it a minor third.

C to E: count C♯ (1), D (2), D♯ (3), E (4). G to B: count G♯ (1), A (2), A♯ (3), B (4). Four half steps make a major third.

Among the white keys, only three 3rds are major: C–E, F–A and G–B. They are the bottom intervals of the three primary chords of C major (C, F and G). Every other 3rd needs an accidental to become major: D–F♯, E–G♯, A–C♯, B–D♯.

Major thirds in chords

A major triad is a major third with a minor third on top: C–E–G. The augmented triad stacks two major thirds (C–E–G♯). Add a third major third and you arrive at B♯, the same key as C: three major thirds divide the octave into three equal parts.

How it sounds

The major third is the sound of "major": bright, open and settled. A rising major third opens "When the Saints Go Marching In" (on "Oh when"), and many two-tone doorbells play a falling one. Harmonically it is a consonance (an imperfect consonance in classical theory).

An acoustically pure major third has a frequency ratio of 5:4, about 386 cents. The equal-tempered major third on a piano is about 14 cents wider. Choirs and string quartets tend to tune sustained major thirds narrower than the piano does, closer to the pure ratio (see just intonation).

Inversion and look-alikes

Inverted, a major third becomes a minor sixth: C–E becomes E–C, and 4 + 8 = 12. The same distance spelled with letters four apart forms a diminished fourth. It is rare, but real: in A harmonic minor, G♯ up to C is a diminished fourth.

Practice with Major & minor 2nds and 3rds and Intervals: steps & skips.

Common questions

How many half steps are in a major third?

Four. From C: C♯ (1), D (2), D♯ (3), E (4). A minor third has three.

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

Both span three letter names, but a major third is one half step wider: four half steps (C–E) instead of three (C–E♭). That single half step decides whether a triad built on the lower note is major or minor.