Seam Allowance Calculator — Total Fabric with Seam Allowances

In the UK, most commercial patterns include 1.5 cm (5/8 inch) seam allowance. Some independent pattern companies use 1 cm. Japanese patterns often include no seam allowance at all, requiring you to add your own.

Ease is the gap between your BODY measurement and the finished garment. Enter your body bust/waist/hip, then add ease: for woven fabrics close-fitting 2-3 cm, standard fit 5-8 cm, loose fit 10-15 cm (measured around the full girth). For knits with good stretch, ease can be zero or negative (compression garments) — the calculator adds ease, then applies the stretch factor.

Knit fabrics often use 1 cm seam allowance instead of 1.5 cm, as the stretch handles fit adjustments. Set the stretch factor below 1.0 in Advanced Options to cut pieces smaller than the body measurement — a 0.85 factor gives roughly 15% negative ease, so a stretchy garment hugs the body rather than hanging loose.

A 301 lockstitch uses about 2.5 times the seam length in total — the needle and bobbin each consume roughly 1.25 times the seam length (Coats Thread Consumption Guide) — so allow around 2.75 times once ~10% waste is included. A typical blouse uses 100-150 metres, a dress 150-250 metres. Chainstitch and overlocked seams use far more: a 401 two-thread chainstitch is around 5.5× the seam length, and a 4-thread overlocker roughly 18× per seam, so buy several cones.

No, hems are typically wider: 3 cm for a standard turned hem, 5 cm for a deep hem, 1-2 cm for a narrow rolled hem. This calculator separates hem allowance from seam allowance.