What Is a Perfect Fifth?

A perfect fifth is an interval of seven half steps — A up to E, or C up to G. After the octave, it's the most stable, consonant interval in music: so neutral and strong that a root and fifth alone (a power chord) works for entire genres.

The shape every guitarist already knows

From the low E or A string: one string up, two frets up. It's the power chord shape:

Why fifths run the show

• Every major and minor triad contains a perfect fifth — it's the neutral frame; the third inside it picks the mood.
• Stack fifths and you generate every key: that's literally the circle of fifths.
• The fifth scale degree — the dominant — creates the strongest pull back home in all of harmony.
• Acoustically it's the first non-octave interval in the harmonic series, which is why it sounds so solid.

Ear anchor: the opening of "Twinkle, Twinkle, Little Star" (more interval songs).

Related terms

• Perfect fourth — its inversion
• Tritone — the unstable interval one half step below it
• Dominant — the fifth degree of the scale