How to use

1. Select a fabric type from the reference table (cotton, linen, viscose, wool) or enter custom values.
2. Cut a 20×20 cm swatch and mark exact test dimensions before washing.
3. Wash or steam press the swatch using the same conditions as future garment care.
4. Measure the swatch after drying and enter post-wash dimensions (L1, W1).
5. Receive warp and weft shrinkage percentages and the exact pre-shrink purchase yardage.

Why Fabrics Shrink & Which Materials Shrink Most

Fabric shrinkage occurs when fibers relax upon contact with moisture, heat, or mechanical agitation during laundering. Most natural fiber fabrics shrink because yarn tension introduced during weaving or finishing is released.

Manufacturers intentionally leave residual tension in the cloth to make it appear denser. Contact with water releases this tension and the fabric returns to its natural relaxed state.

• Natural linen: 7–12% warp and 4–7% weft — highest shrinkage of all common fabrics;
• Viscose / rayon: 6–9% warp, up to 5% weft;
• Cotton (poplin, sateen, muslin): 4–6% warp;
• Wool and tweed: 4–7%, up to 15–20% in warm water;
• Raw denim: 5–8% without prior shrinking treatment;
• Natural silk: 2–4% with gentle cool water wash;
• Polyester and synthetics: under 1% — virtually shrink-proof.

How to Accurately Measure Fabric Shrinkage at Home

The most reliable way to measure actual shrinkage is a swatch test on a small piece of fabric before cutting your fashion fabric.

• Cut a 25×25 cm swatch (identify warp and weft grain direction);
• Mark precise 20×20 cm test dimensions with chalk or contrasting thread;
• Launder the swatch using the same washing method as the finished garment will require;
• After line drying, measure the marked test area — the difference is shrinkage;
• Enter the measurements into the calculator for accurate purchase yardage.

What is Preshrinking (Decatizing) & When is it Required?

Preshrinking (also called decatizing) is the deliberate pre-treatment of fabric with moisture and heat before cutting, to relax fiber tension and stabilize dimensions.

Always preshrink cotton, linen, wool, and blended fabrics before cutting. Synthetic fabrics generally do not require preshrinking.

• Steam pressing: dampen fabric with a wet press cloth and iron on grain with steam;
• Wet soak: submerge fabric in room-temperature water for 30–60 minutes, gently squeeze, and dry flat;
• Machine wash: launder fabric using the same cycle as the intended garment care label;
• Industrial decatizing (boiler press): required for high-end tailoring wool and suiting cloths.

How Much Extra Yardage to Buy to Account for Shrinkage

To ensure your finished garment retains its pattern piece measurements after the first wash, purchase additional yardage corresponding to the shrinkage percentage of your fabric.

• Linen, raw cotton muslin: up to 15% extra yardage;
• Cotton, viscose/rayon: 7–10%;
• Wool, knit jersey: 5–8%;
• Silk, lightweight polyester blend: 3–5%;
• Pre-washed / Sanforized fabrics: only 2–3% allowance needed.