UPF ultra violet factor stands for ultra violet protection factor
It is the fabric's ability to avoid and repel the harmful effects of ultraviolet rays.
The UPF has several ranks of protection indicated by a number 20, 30, 50 and 50+.
Currently the UPF50+ is the maximum existing certification.
This means that the garment protects covered areas up to 98% against UV-A and UV-B radiation.