Hem Allowance Calculator
How much extra length to cut below the finished hemline, by hem style.
Get a Cleaner Hem Fold
A hem foot attachment rolls and folds narrow hems as you sew, instead of pressing and pinning each turn by hand.
Cut length = finished length + hem allowance
The hem allowance is the extra fabric folded up (once or twice) below the finished hemline to enclose the raw edge. A narrow rolled hem only needs about 1/4", while a deep hem on a formal or lined garment might use 2–3" for extra weight and structure at the hemline.
Facings don't need a hem allowance
If a garment's hem is finished with a separate facing piece rather than folding the garment fabric itself, don't add hem allowance to the main pattern piece — the facing handles the raw edge instead, and adding both would make the garment too long.
Hem allowance and curved hems
Deep hem allowances get harder to turn under smoothly on a curved hemline (like a circle skirt) because the folded edge has more fabric to ease in than the hemline it's being turned onto. Use a narrower hem allowance (1/4–1/2") on strongly curved hems even if you'd otherwise prefer something deeper.