Sixths can be major, minor, augmented or diminished. Below you can see that the number of steps determines the quality of the interval:
Major sixth, 4 1/2 whole steps or 9 half steps:
Minor sixth, 4 whole steps or 8 half steps:
Augmented sixth, 5 whole steps or 10 half steps:
Diminished sixth, 3 1/2 whole steps or 7 half steps:
The easiest way to determine the quality of a sixth is to invert the interval and identify the resulting third. For example, the interval C#-A#:
See I > Intervals for related entries. To learn about go to Tutorials > Intervals.