Diminished fifth, 3 whole steps or 6 half steps
Perfect fifth, 3 1/2 whole steps or 7 half steps
Augmented fifth, 4 whole steps or 8 half steps
When analyzing the quality of a fifth we should know that:
- the interval is a perfect fifth if all the notes are natural, with the exception of the fifth B-F, which is a diminished fifth.
If there are accidentals you should identify the interval without accidentals and then analyze the effect of the accidentals.
Another example: Gb-Db:
Identifying fifths by counting whole and half steps is slow and confusing. See Simplifying accidentals.