Definition
A crotch curve is the curved seam of trousers and shorts that runs from the front waist down between the legs and up to the back waist.
The crotch curve is the part of a trouser pattern that most affects comfort and fit. It has two halves: the front crotch curve, short and fairly upright, and the back crotch curve, longer, deeper and set at an angle to make room for the seat.
Its shape depends on two body measurements:
- Crotch depth, or body rise: sitting on a hard chair, from the waist at the side down to the seat (see rise).
- Crotch length: from the center front waist, between the legs, to the center back waist, measured with a tape.
Signs of a curve that does not suit you: pulling or a wedgie means the crotch is too short or too shallow; folds hanging below the seat and a low, saggy crotch mean it is too long or too deep. Changes are made on the pattern by adding or removing length at the lengthen line and reshaping the lower curve, then tested on a toile.
Sew the crotch seam twice, or with a narrow stretch stitch on knits, because it takes strain, and clip the curve below the notches. Elastic-waist pull-on trousers and shorts are the easiest way to learn how a crotch curve fits you, since there is no zip or fly front to deal with. Related seams: the inseam and the outseam.