Perfect fifth
(重定向自Diapente)

![Just perfect fifth on D Play . The perfect fifth above D (A+, 27/16) is a syntonic comma (81/80 or 21.5 cents) higher than the just major sixth above middle C: (A♮, 5/3).[9]](/uploads/202501/08/Just_perfect_fifth_on_D3219.png)
![Just perfect fifth below A Play . The perfect fifth below A (D-, 10/9) is a syntonic comma lower than the just/Pythagorean major second above middle C: (D♮, 9/8).[9]](/uploads/202501/08/Just_perfect_fifth_below_A3219.png)
In music theory, a perfect fifth is the musical interval corresponding to a pair of pitches with a frequency ratio of 3:2, or very nearly so.
In classical music from Western culture, a fifth is the interval from the first to the last of five consecutive notes in a diatonic scale. The perfect fifth (often abbreviated P5) spans seven semitones, while the diminished fifth spans six and the augmented fifth spans eight semitones. For example, the interval from C to G is a perfect fifth, as the note G lies seven semitones above C. Play