Which fibres grow the most when blocked?

Superwash wool and alpaca tend to grow the most, especially in length. Regular wool grows moderately. Cotton and linen can actually shrink slightly. Acrylic barely changes with wet blocking but responds to steam. Always block your gauge swatch to know exactly how your specific yarn behaves.

Should I knit smaller if my yarn grows when blocked?

Yes. If you know your yarn grows 10% after blocking, you should knit your piece to be about 10% smaller than the target finished size. Alternatively, match your gauge on a blocked swatch so the pattern measurements will work without further adjustment.

What is the best way to block knitting?

Wet blocking: soak in lukewarm water for 20 minutes, gently squeeze out water (never wring), roll in a towel, then pin to shape on blocking mats. Steam blocking: hold a steam iron above the fabric without touching it. Spray blocking: mist with water and pin to shape. Different fibres respond best to different methods.

KnitCalcs

Blocked vs Unblocked Calculator — Size Change After Blocking

Estimate how much your knitted piece will grow or shrink after blocking based on fibre type.

Unblocked Width

Unblocked Length

Fibre Type

How We Calculate This

This calculator applies typical growth or shrinkage rates for different fibre types to estimate blocked dimensions.

The formula

Blocked size = Unblocked size x (1 + Growth rate %)

Growth rates are ranges because the exact change depends on many factors: tension, stitch pattern, how aggressively you block, and the specific yarn. The calculator gives a minimum and maximum estimate.

Frequently Asked Questions

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Last updated: February 2026

All calculations are estimates based on standard yarn weights and gauge. Results may vary with individual tension, yarn brand, and needle size.