Inverting Intervals
Flip an interval upside down — move the bottom note up an octave — and it becomes a new interval that follows two simple, predictable rules.
Rule 1: the number
To invert an interval's number, subtract it from 9. A 2nd inverts to a 7th, a 3rd to a 6th, a 4th to a 5th, and a unison to an octave (and vice versa). This works because the two interval numbers always add up to 9 — one note's letter-distance up, the other's letter-distance down, across the same octave.
Rule 2: the quality
Major and minor swap: a major interval inverts to minor, and minor inverts to major. Augmented and diminished swap the same way. Perfect intervals are the one exception — a perfect interval always inverts to another perfect interval.
Common questions
What is the rule for inverting an interval's number?
Subtract the original number from 9 — a 2nd inverts to a 7th, a 3rd to a 6th, a 4th to a 5th, a unison to an octave.
What happens to the quality when you invert an interval?
Major and minor swap, augmented and diminished swap. Perfect intervals stay perfect.
How do you actually invert an interval?
Move the bottom note up an octave (or the top note down an octave) so the two notes swap which one sits on the bottom.
Why does the tritone stay a tritone when inverted?
Because it exactly splits the octave in half, it's the one interval identical to its own inversion.
Flip intervals until it's instinct
Melody Monkey's Ear Training tool quizzes inversions alongside every other interval skill.
Open the ear trainer →Still stuck? Ask Your Personal Music Teacher about Inverting Intervals →