Sewing Seam Allowance Calculator

Summary

Enter your finished garment dimensions and seam allowance to get exact fabric cutting sizes.

How it works

1. Enter the finished (sewn) width and height for each garment piece.
2. Select your preferred unit — inches or centimeters.
3. Set the seam allowance value (e.g. 0.5 in or 1.5 cm).
4. Choose whether to apply the allowance to all sides or specify per-side values.
5. Click Calculate to see the cutting dimensions and total fabric area.
6. Use the Copy Results button to export measurements for your pattern sheet.

Use cases

• Calculate cutting size when drafting a garment pattern from scratch.
• Convert finished measurements from a commercial pattern to cutting dimensions.
• Quickly adjust seam allowances when switching between pattern styles.
• Compute fabric requirements for multiple pieces in a single session.
• Double-check hand-drafted pattern pieces before cutting expensive fabric.
• Scale seam allowances when grading a pattern up or down.

Frequently Asked Questions