Tools you might need next
Calculate how many yards of fabric you need for a sewing project. Plan pattern layout, width, and repeats to buy the right amount of material.
Calculate quilt backing fabric needed including overhang and seam allowance. Size backing for longarm, domestic machine, or hand quilting projects.
Calculate seam allowance adjustments for pattern alterations and garment fitting. Add or subtract ease when resizing or modifying sewing patterns.
Cut elastic shorter than body measurement so it stretches to fit snugly. Percent reduction depends on elastic type and comfort preference.
Cut length = body measurement × (1 − reduction fraction)Elastic rated 50% stretch extends to 150% of relaxed length. Match reduction to elastic specs and garment ease.
Stretched length = cut length × (1 + stretch %)Serged or zigzagged joins need ½–1 inch overlap subtracted from cut length or added to casing allowance.
Final waist = cut length + overlap − casing easeUpdated: July 2026
Cut woven elastic at 90% of waist (27 inches) for firm hold; knit elastic at 85% for softer gather on lightweight fabric.
Comfort fit often uses 95% of waist measurement with soft knit elastic — calculator adjusts for preferred reduction.
Ankle circumference 8 inches with 10% reduction → 7.2-inch cut plus ½-inch overlap for join.
Elastic must be shorter so it tensioned in wear. Exact body length feels loose and slides down.
Cuffs often need less reduction (5–8%) than gathered waistbands (15–25%) — match elastic function and fabric weight.
Elastic waistbands and cuffs need cut lengths shorter than the body measurement so tension holds the garment in place. Enter body circumference, desired ease, and elastic stretch percent to find the correct cut length for woven or knit elastic.