The UPF rating system is very similar to the system used to rate sunscreens…the SPF system. The Ultraviolet Protection Factor (UPF) measures the penetration of Ultraviolet rays through fabric.

A UPF rating of 50 means that a given piece of fabric allows 1/50 of the UV rays that hit it to penetrate through. This is the same as 98% UV protection.

The garments you see on this web site that are labeled UPF 50 or UPF 50+ are certified to block the sun’s rays as set forth above.