Seam Allowance Calculator

Convert Between Seam Allowances

Pattern Includes (SA)

You Want (SA)

Pattern Piece Measurement (edge to edge, including SA) Unit

Standard Seam Allowances by Region

Standard	Seam Allowance	Common In
US Commercial	5/8" (1.6cm)	Big 4 patterns (Simplicity, McCall's, Butterick, Vogue)
EU / Asian	1cm (3/8")	Burda, Japanese patterns, indie EU designers
Indie US	Varies (3/8"-1/2")	Many independent pattern companies
Quilting	1/4" (6mm)	All quilting patterns
Serger/Overlock	3/8" (1cm)	Knit patterns using serger
French Seam	5/8" (1.6cm)	Delicate fabrics, sheer materials
Flat-felled	5/8"-1" (1.6-2.5cm)	Jeans, shirts, heavy-duty seams

Tip: Always check your pattern instructions for the included seam allowance before cutting. Japanese patterns often include no SA -- you must add your own. Mark your seam line on the fabric for accurate sewing.