What is ease in a sewing pattern?

Ease is the difference between your body measurement and the finished garment measurement. It is designed in, not an error.

Two kinds.

Wearing ease is what lets you move, breathe and raise your arms. A fitted bodice typically has 5 to 10 cm of wearing ease at the bust. Without it you could not sit down.

Design ease is everything beyond that — what makes an oversized shirt oversized. A relaxed jacket might have 20 cm or more, and that is the design.

Why it matters when choosing a size. People measure themselves, see that the pattern’s finished bust is 12 cm larger, conclude the pattern runs big, and size down. The result is a garment with no wearing ease that cannot be worn comfortably.

How to use it properly. Most patterns print the finished garment measurements on the pattern piece itself. Compare that to a garment you already own and like — measure the flat garment across the bust and double it. That tells you how the pattern will actually fit, far more reliably than the size chart.

Negative ease exists too, on knits: the finished garment is smaller than the body and stretches to fit. Sizing up “to be safe” on a knit pattern produces something baggy.