Sevenths can be major, minor, augmented or diminished. Below you can that the number of steps determines the quality of the interval:
Major seventh, 5 1/2 whole steps or 11 half steps:
Minor seventh, 5 whole steps or 10 half steps:
Augmented seventh, 6 whole steps or 12 half steps:
Diminished seventh, 4 1/2 whole steps or 9 half steps:
The easiest way to identify the quality of a seventh is by inverting the interval and identifying the resulting second. For example, the interval C-B:
The inversion of a major 7th results in a minor 2nd
See I > Intervals for related entries. To learn about go to Tutorials > Intervals.