1020 thigh oversized
grasp the thighs on both sides (+/- 10 cm under the crotch) and give the oversize you want between your fingers. (give the double folded distance from 1 side) keep symmetry in mind (the same amount on both sides).
For a straight leg we advise 2 cm  so you have comfort,
For a tapered or bootcut you can take less, keep in mind we don't sell stretch fabrics.