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:

Identifying Sixths

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#:

1. Sixth interval
2. Becomes a third when inverted.
3. A#-C# is a minor third so C#-A# is a major sixth (see inversion of intervals).