UPF stands for Ultraviolet Protection Factor and is used to provide
information about the level of protection that garments provide. Clothes
with a UPF 50+ rating block out 97.5% of UVA and UVB rays. This is a
level of protection that is approximately 5 times higher than that
provided by a normal cotton T-shirt. UPF in garments is reached through
a combination of chemical treatment to the yarn and physical properties
of the fabric. The chemical used to treat the yarn follows H&M’s
strict chemical restriction.