Definition
Design ease is the extra room a designer adds beyond wearing ease to create a garment's silhouette, from a slightly relaxed fit to a boxy or oversized shape.
Wearing ease makes a garment wearable; design ease makes it look the way it does. A close-fitting sheath has almost none, a boxy top may add 15 cm (6 in) at the bust, and an oversized sweatshirt 25 cm (10 in) or more. Gathered and circle skirts take it to the extreme: their hem can be several times the hip measurement.
Design ease is not spread evenly. A relaxed top can be roomy at the waist and hem while staying close at the neck and shoulders, and a drop shoulder moves extra width into the shoulder line itself. That is why you should choose your size from your body measurements and then read the finished garment measurements: if you size down to remove ease, you also lose the proportions the design depends on.
Two garments made from the same measurements can differ only in design ease. In Sewly, switching the fit option of a garment, for instance from fitted to oversized, changes this ease and redraws the pattern instantly.
Read more in ease in sewing patterns, or compare typical amounts in the ease chart by garment type.