Remember, perfect intervals have only one basic form. The first (also called prime or unison), fourth, fifth and eighth (or octave) are all perfect intervals. On the other hand, non-perfect intervals have two basic forms. The second, third, sixth and seventh are non-perfect intervals; it can either be a major or minor interval. Major intervals comes from the major scale. Minor intervals are exactly a half-step lower than major intervals.

Here's a handy table that will make it easier for you to determine intervals by counting the distance of one note to another note in half steps.

Table of Intervals

Perfect Intervals
Type of Interval	Number of Half-steps
Unison	not applicable
Perfect 4th	5
Perfect 5th	7
Perfect Octave	12

Major Intervals
Type of Interval	Number of Half-steps
Major 2nd	2
Major 3rd	4
Major 6th	9
Major 7th	11

Minor Intervals
Type of Interval	Number of Half-steps
Minor 2nd	1
Minor 3rd	3
Minor 6th	8
Minor 7th	10