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Fabric shrinkage calculator

Dimensional change after washing in each direction, with growth reported as growth - not forced into a shrinkage number.

Results update as you type.

Inputs

Distance between benchmark marks along the warp / wale.

Distance between benchmark marks along the weft / course.

Result

Lengthwise change

-3%

3% shrinkage

Widthwise change

1%

1% growth

Area change

-2.03%

2.03% shrinkage

Negative values are shrinkage and positive values are growth, the sign convention used by ISO 5077 and AATCC TM135. Growth is a real result, not an input error.

How this is calculated

For each direction, change % = (after − before) ÷ before × 100. Area change is (length after × width after) ÷ (length before × width before) − 1, which is not simply the sum of the two percentages.

Worked example. Benchmarks of 50 cm measure 48.5 cm lengthwise and 50.5 cm widthwise after washing. Length: (48.5 − 50) ÷ 50 = −3.00% (3% shrinkage). Width: (50.5 − 50) ÷ 50 = +1.00% (1% growth). Area: 48.5 × 50.5 ÷ 2,500 − 1 = −2.03%.

Questions

Why are my results negative?
Negative dimensional change is shrinkage; positive is growth. That is the sign convention of ISO 5077 and AATCC TM135, so the numbers can be compared directly with a lab report.
Is growth a bad measurement?
Not necessarily. Knits often grow in width while shrinking in length, and some finishes relax outward. It is reported as a real result.
What benchmark distance should I mark?
Test methods typically mark 350 mm or 500 mm (or 18 in) benchmarks on a larger specimen. Longer benchmarks reduce the relative error of your measurement.

Sources & verification

Specimen marking and the dimensional-change formula follow ISO 3759 and ISO 5077; AATCC Test Method 135 uses the same definition for home laundering. The worked example is recomputed in the automated tests.