Seam Allowance Calculator
Seam Allowance Calculator: From Finished Size to Cut Size
Patterns are drafted around the finished, sewn size of a garment or project piece, but you have to cut the fabric bigger to leave room for the seam itself. This calculator adds the seam allowance to both dimensions to give you the actual cut size.
The Formula
Cut Size = Finished Size + (2 × Seam Allowance)
Worked Example
A 10"×15" finished piece with a standard 5/8" (0.625") seam allowance.
Cut Width = 10 + 1.25 = 11.25", Cut Length = 15 + 1.25 = 16.25"
How to Use This Calculator
- Enter the finished width and length in inches.
- Optionally adjust the seam allowance (5/8" is the standard commercial pattern default).
- Click Calculate to get the cut size.
Related Calculations
Feed the result into the Fabric Yardage Calculator to determine total fabric needed.