UPF Rating Frequently Asked Questions
Short answers to the questions buyers ask most often about UPF Rating.
What does it mean?
ultraviolet protection factor of fabric. Working figures for UPF Rating normally sit around UPF 50+ blocks over 97.5% UV in mainstream production. Note AATCC 183 or EN 13758 on the tech pack so nobody tests against an older revision.
What value should be specified?
Start from UPF 50+ blocks over 97.5% UV and adjust for the end use of the garment. Record elastane content alongside UPF Rating, because blends shift the measured value. A result outside UPF 50+ blocks over 97.5% UV usually points to process drift rather than to the fibre itself.
How is it tested?
AATCC 183 or EN 13758. Keeping reference values for UPF Rating lets suppliers quote without extra sampling rounds. Ask for conditioning details together with AATCC 183 or EN 13758, since both affect the reading.
Why does it change between lots?
Process variables such as finishing temperature and elastane batch cause the normal spread of results. Working figures for UPF Rating normally sit around UPF 50+ blocks over 97.5% UV in mainstream production. Note AATCC 183 or EN 13758 on the tech pack so nobody tests against an older revision.
Can results be compared across suppliers?
Only when the same standard revision and conditioning are used; otherwise measurements are not equivalent. Record elastane content alongside UPF Rating, because blends shift the measured value. A result outside UPF 50+ blocks over 97.5% UV usually points to process drift rather than to the fibre itself.
