Does wool grow or shrink when blocked?

Wool typically grows 5-10% when wet blocked, especially in width. The fibres relax and the fabric opens up. This is why many wool garments are knitted slightly smaller than the finished measurements. Superwash wool may grow even more as it lacks the scales that hold the fibres together.

Does cotton grow or shrink when blocked?

Cotton tends to shrink 2-5% when washed and blocked, particularly in length. Unlike wool, cotton does not have elastic memory, so it does not bounce back. Knit cotton garments slightly larger than target to account for shrinkage.

What is the difference between wet, steam, and spray blocking?

Wet blocking (soaking the piece) has the most dramatic effect on size and shape. Steam blocking gives a moderate effect and works well for wool. Spray blocking (misting and pinning) has the mildest effect and is best for acrylic and items that need minimal reshaping.

Should I always block my knitting?

Blocking evens out stitches, opens up lace, relaxes cables, and gives a professional finish. Most garments benefit from blocking. The exception is ribbing and textured stitches where you want the fabric to remain elastic and springy.

KnitCalcs

Blocking Shrinkage Predictor — Size Change After Blocking

Predict how blocking will change the size of your knitted piece based on fiber content and method.

Fiber Content

Select an option for fiber content

Blocking Method

Select the method

Current Stitch Gauge (per 10cm)

Stitches per 10cm from your gauge swatch

Current Row Gauge (per 10cm)

Rows per 10cm from your gauge swatch

Piece Width

Width measurement

Piece Height

Height measurement

How We Calculate This

This calculator estimates size change after blocking based on fiber properties and the blocking method used. Each fiber reacts differently to moisture and heat.

Typical blocking changes

Wool: grows 5-10% (wet block)
Cotton: shrinks 2-5%
Acrylic: minimal change
Alpaca: grows 10-15% (drapes significantly)

Frequently Asked Questions

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Last updated: March 2026

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