oh, on a funny sidenote, I made the girls figure out the size of each circle... they looked at me horrified! I said "but I've got the waist measurements"... they were like deer caught in the headlights! LOL
It's easy, if anyone has to figure it out...
waist divided by pi, divided by 2 (24" waist = 3.82 radius)
then add the measurement from waist to knee...
then add 3" for covering the knee...
x2 gives you the yardage you'll need...
craft felt is 72" wide, so this particular girls skirt needed a 49" circle cut.
We re-folded the felt to make a 49x49 square we were cutting from...
This leaves a long piece that you get your waistband from :)