Seam allowance calculator
Add seam allowances to a simple rectangular finished panel.
How it works
Cut dimensions equal finished dimensions plus twice the seam allowance. This simple model does not add hems, overlap, seam finishing, shrinkage, or ease. Follow your actual sewing pattern if the allowance is already included.
A worked example
A 40 × 40 cm finished rectangle with 1.5 cm on each edge requires a 43 × 43 cm cut piece. Adding it twice to a commercial pattern that already includes it will oversize the piece.