To write intervals, memorize the following: Music Fundamentals   William Wieland
Augmented (A)
Major (M)
minor (mi)
diminished (d)
( 2, 3, 6, 7 )
Augmented (A)
Perfect (P)
diminished (d)
( 1, 4, 5, 8 )
P8 same name
M7 almost an octave (half step smaller) Sevenths Diagram
mi7 close to an octave (whole step smaller) Sevenths Diagram
M6 M2 larger than a P5
mi6 mi2 larger than a P5
P5 root to 5th of any major triad or minor triad Circle of 5ths Perfect Fifths at the Keyboard
P4 whole step smaller than a P5 The Circle of 5ths is also the circle of 4ths.
M3 root to 3rd of any major triad 1 to 3 of any major scale or major key
mi3 root to 3rd of any minor triad 1 to 3 of any minor scale (natural, harmonic or melodic) or minor key
M2 whole step
mi2 half step
P1 identical pitch
 
    The major scale method: do
ti
la
sol
fa
mi
re
do do do do do do do
    M2         M3         P4         P5         M6         M7         P8