Blocking Measurements Calculator — Target Dimensions After Blocking

These are typical rules of thumb, not fixed values — superwash wool grows far more than untreated, and lace can open up 20-30%. As a guide: wool 10-15%, cotton and linen only 3-5%, acrylic barely moves and springs back. Alpaca and silk are different: they stretch very easily but have little or no "memory", so they will not spring back and can keep growing under their own weight. Silk in particular can physically grow ~20% but will sag if hung wet, so the safe target before permanent distortion is much lower — the calculator caps silk at 8% as a conservative "hold this shape" limit rather than how far it can go. Always block a swatch and measure before and after to get your own yarn's real stretch factor.

Wool can be blocked to a slightly smaller size by encouraging it to relax rather than stretch. Cotton does not shrink much with blocking. Acrylic responds to steam (called "killing" the acrylic) but this is permanent and cannot be reversed.

Wet blocking: soak in lukewarm water with wool wash for 20 minutes, gently squeeze out water (no wringing), pin to measurements on blocking mats, and let dry completely. This gives the most control over final dimensions.

Most projects benefit from blocking. It evens out stitches, opens up lace patterns, relaxes ribbing, and brings the piece to the correct dimensions. Garments, shawls, and lace should always be blocked. Simple scarves and hats may not need it.

Depends on fibre, thickness, and humidity. Thin wool pieces may dry in 12-24 hours. Thick cotton blankets can take 2-3 days. Use fans to speed drying. Avoid direct sunlight which can fade colours. Do not unpin until completely dry.