Two methods, and one measurement rule that applies to both.
Cut the elastic to the body, not the garment. For a waist, roughly the waist measurement less 5 to 10 percent depending on how much recovery the elastic has. Pin it into a loop and try it before cutting the tail — elastic varies between batches.
Join it properly. Overlap the ends by about 15 mm and sew a box with a cross through it, or a wide zigzag across the overlap. A butted join with a single straight row has nothing to stretch and will fail.
Method one: casing. Sew a folded channel at the waist, leave a gap, thread the elastic through with a safety pin or a bodkin, join, and close the gap. Simple, and the elastic can be replaced later.
Method two: stitched directly. Quarter-mark both the elastic and the waistband with pins. Match the quarters, then stretch the elastic to fit between each pair of marks while sewing with a zigzag or a three-step zigzag. Quarter-marking is what makes the gathering even.
Do not stretch the fabric, only the elastic. And use a stretch stitch or a zigzag — a straight stitch across elastic snaps the first time it is worn.
Questions people actually ask
My elastic twists inside the casing.
Common with narrow elastic in a wide casing. Stitch through the casing and elastic at the side seams to anchor it, or use wider elastic.
How tight should elastic be?
Snug but not marking the skin. Pin it around yourself before cutting — the percentages are a starting point, not a rule.
Last reviewed 2026-08-11