The Ultraviolet Protection Factor (or “UPF”) rating measures the UV protection provided by a fabric. It is similar to the SPF rating used for sunscreens. Berry Jane™ rash guards, swim leggings and swimsuits rating is UPF 50, which is the highest possible rating. That means it only allows 1/50th of the UV radiation to pass through it — blocking 98% of harmful rays.
Keep in mind, no clothing can completely block all UV rays so the use of sunscreen is still recommended. Several factors that may affect the level of UV protection include fabric color and weight. Most fabrics lose some of their UV protection if the garment is stretched out or worn, or if it has been washed repeatedly. Lighter colors also tend to lose more of their sun protection when damp or wet than darker colors.