Seam Allowance Calculator for Cut Size
Add seam allowance to a finished measurement to get the size to cut. The allowance sits on every edge, so each dimension grows by twice the allowance.
How to add seam allowance
- Enter the finished width and height of the piece in inches.
- Set the seam allowance for each edge, often 1/4 or 1/2 inch.
- Read the cut width and height, then copy the dimensions.
Examples
10 by 12 inch finished with a 1/2 inch allowance
Finished 10 x 12 in, seam allowance 0.5 in
Cut 11 x 13 in
Frequently asked questions
How do I add seam allowance to a pattern?
Add the seam allowance to both opposing edges of each dimension. A piece grows by twice the allowance in width and twice in height, so a 1/2 inch allowance adds 1 inch to each measurement.
What is a standard seam allowance?
Garment sewing usually uses 5/8 inch, quilting uses 1/4 inch, and many home projects use 1/2 inch. Use whatever your pattern specifies so the finished size comes out right.
Finished size or cut size, which goes in the pattern?
Patterns list both. Finished size is the piece after sewing; cut size includes the allowance. Cut to the cut size, then sew on the seam line to reach the finished size.
Does this handle the allowance on all four sides?
Yes. The allowance is added to every edge, so each dimension is increased by two allowances. Enter a zero allowance to cut exactly on the finished line.
What about hems and facings?
Those need extra beyond the seam allowance. Add hem and facing depth separately to the relevant edges, since they are usually wider than a normal seam allowance.
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