Wearing it
Sun shirts, swim trunks and what UPF means
Every sun shirt in the range carries a UPF number on its label. It rates the cloth, not a sunscreen, and the number means something specific. Here is the wording from the people who set the bar, and what we can say about our own cloth.
Start with the piece
BOJIN tees & sun shirts to look at first
Blue Gradient Rash Guard, 060A
88% polyester, 12% spandex · long sleeve
Size L
4.7 out of 5 from 40 ratings
$5.99
What the number is
UPF stands for ultraviolet protection factor. A lab measures it on the cloth before anyone sews the shirt. The definition is short.
Ultraviolet Protection Factor (UPF) indicates how much UV radiation (both UVB and UVA) a fabric allows to reach your skin.The Skin Cancer Foundation, Sun-protective clothing, read 4 September 2026
For example, a UPF 50 fabric blocks 98 percent of the sun’s rays and allows two percent (1/50th) to penetrate, thus reducing your exposure risk significantly.The Skin Cancer Foundation, Sun-protective clothing, read 4 September 2026
How the ratings rank
The same source ranks the bands: a UPF of 30 to 49 is called very good, and 50 and above excellent. The maker prints the rating on the label of each sun shirt, and the specification on its page repeats that number as the maker's, not as a test we ran.
Ratings on the labels in the range
| UPF 50+ | 12 pieces carry this rating on the label |
|---|
Sun shirts and rash guards
Orange Gradient Rash Guard
88% polyester, 12% spandex · long sleeve
4.6 out of 5 from 31 ratings
$5.99 this size
Cloth, colour and fit change the number
The lab rates new, dry, unstretched cloth. Stretch a rash guard over a wide back and the weave opens a little. Soak it and the rating changes again. Darker, tighter knits hold their rating better than pale loose ones, so most of ours come in mid to dark tones with a close cut.
None of that turns a shirt into sunscreen. The federal advice puts clothing first on the list and then adds the rest.
Wearing clothing to cover skin exposed to the sun, such as long-sleeve shirts, pants, sunglasses, and broad-brim hats.U.S. Food and Drug Administration, Tips to stay safe in the sun, read 4 September 2026
Swim trunks are not sun shirts
The trunks on the same bench are a quick-dry polyester with a mesh liner and a drawcord. The label carries no UPF rating, so the page prints none. What they do is dry on a chair by lunch and keep their colour through a season of chlorine, which is what the maker states and what we have seen.
This is not medical advice
Everything above is general information from the sources listed below, read on the date shown. It is not a diagnosis and it is not a substitute for a doctor or a dermatologist. If skin burns through a shirt, or a mole changes, that is a question for a clinician rather than a clothing catalogue.
Before you go
More tees & sun shirts in the range
Orange Gradient Rash Guard
88% polyester, 12% spandex · long sleeve
4.6 out of 5 from 31 ratings
$5.99 this size
Black Gradient Rash Guard
88% polyester, 12% spandex · long sleeve
Size XL
4.6 out of 5 from 31 ratings
$5.99
Sources
- Sun-protective clothing, The Skin Cancer Foundation, read 4 September 2026
- Tips to stay safe in the sun, U.S. Food and Drug Administration, read 4 September 2026