2 Half steps
A pentatonic scale is made up of 5 notes, and can be hemitonic (containing half steps) or anhemitonic (not containing half steps).
5
2
The semitones (half steps) in a major scale are between the 3rd and 4th and the 7th and 8th notes.
The chromatic scale is made up entirely of half steps.
The chromatic scale
2 Half steps
A pentatonic scale is made up of 5 notes, and can be hemitonic (containing half steps) or anhemitonic (not containing half steps).
2
5
The chromatic scale
That's a chromatic scale.
The major scale is made of whole and half steps. WWHWWWH
The semitones (half steps) in a major scale are between the 3rd and 4th and the 7th and 8th notes.
The chromatic scale is all half-steps, so no formula is required.
A Chromatic scale starting from any of the 12 notes, in full, will have 13 half steps.