The girls' all time favorite skirts are not doing it anymore: too tight, too short. However, they lasted a full 3 (!!!!) years.
I told the girls they could wear the skirt either way: pockets in front or back: K now ALWAYS wears hers with the pockets in back and A ALWAYS wears hers with the pockets in front. (Sorry, that's funny to me.)
Farbenmix' free pattern. That would save you the calculating part!