Sewing calculator

Seam and Hem Allowance Calculator

Turn finished dimensions into cut dimensions with independent edge allowances.

Your measurements

Use one unit for every dimension in this form.

Width after sewing.

Height after sewing.

Allowance on the left edge.

Allowance on the right edge.

Allowance on the top edge.

Allowance on the bottom edge.

Seam and hem result

Cut width
43.00 in
Cut height
43.00 in
Finished and cut dimensionsA scaled planning diagram. Use the matching text result and cut list for exact dimensions.Cut rectangleAllowances included
Finished and cut dimensions. The drawing is scaled for comparison; written dimensions control.

Formula

Cut width equals finished width plus left and right allowances; cut height adds top and bottom allowances.

Assumptions

  • Allowances are measured perpendicular to each edge.

When a tested commercial pattern gives different cutting dimensions or layout instructions, follow that pattern.

Worked example

  • 40 × 40 in finished square
  • 1.5 in on each edge

The required cut size is 43 × 43 inches.

Verification note

Confirm whether the source measurement is a finished line or an existing cut line before adding anything.

Learn and verify