interval
D perfect fifth
DlowerAupperP57 half steps
Seven half steps. Stack twelve of them and you land back where you started, give or take a comma.
On the keyboard
What is true of it
D up a perfect fifth is A: 7 half steps, and 5 letters counting both ends.
Turn it upside down — put the D on top — and it becomes a perfect fourth. The two numbers always add to nine, and the two sizes to twelve.
It is a perfect consonance.
Every interval on D
D → E♭minor second · dissonanceD → Emajor second · dissonanceD → Fminor third · imperfect consonanceD → F♯major third · imperfect consonanceD → Gperfect fourth · perfect consonanceD → G♯augmented fourth · dissonanceD → A♭diminished fifth · dissonanceD → B♭minor sixth · imperfect consonanceD → Bmajor sixth · imperfect consonanceD → Cminor seventh · dissonanceD → C♯major seventh · dissonance