Mark the fabric before the wash test, measure again after washing and drying, and enter both. The calculator gives the length and width shrinkage, the GSM the fabric will have after washing, and the spirality.
How it works
- Shrinkage % = (before − after) ÷ before × 100. A minus result means the fabric grew.
- GSM after wash = GSM before ÷ ((1 − length shrinkage) × (1 − width shrinkage)).
- Spirality % = wale displacement ÷ measured length × 100.
Use the same wash and drying method the buyer specifies, and mark at least 35–50 cm in each direction for a reliable reading.
Questions
How do you calculate shrinkage %?
Shrinkage % = (mark distance before wash − after wash) ÷ before wash × 100. A 50 cm mark that measures 47.5 cm after washing has shrunk 5%.
Why does GSM go up after washing?
When the fabric shrinks, the same weight of yarn sits on a smaller area. With 5% length and 4% width shrinkage, a 160 GSM fabric becomes about 175 GSM.
How is spirality calculated?
Spirality % = side seam (wale) displacement ÷ the length it was measured over × 100.