Fourths and fifths are inverse intervals. That means, for example, that when we move up a fifth in order to go back down we move in a fourth. C to G is a fifth, and G to C is a fourth, got it? In the diagram below, you’ll see the moving clockwise moves in fourths, and counterclockwise moves in fifths. You can use this chart to determine inverse intervals by moving the same amount in either direction, i.e. one step clockwise is the inverse of one step counterclockwise, which in this case gives us the fourth and the fifth respectively.
Perfect fourths left to right (7-3-6-2-5-1-4) and perfect fifths right to left (4-1-5-2-6-3-7):
