Ultraviolet Protection Factor (UPF) indicates how much UV radiation a fabric allows to reach your skin. For example, a UPF 50 fabric blocks 98 percent of the sun’s rays and allows two percent to penetrate, thus reducing your exposure risk significantly.
UPF measures the amount of UV radiation that can penetrate fabric and reach your skin. Sun Protection Factor, or SPF, is based on the time it takes for UV-exposed skin to redden. Another important distinction is UPF measures both UVB and UVA rays, while SPF measures only UVB.
Clothing helps shield you from the sun, but not all fabrics and colors provide equal protection. Luckily, you have plenty of options.
The first factor is color, dark or bright colors keep UV rays from reaching your skin by absorbing them, that’s why these colors offer better protection than lighter shades. Densely woven cloth, like denim, canvas, wool, or synthetic fibers, are more protective than a sheer, thin, or loosely woven cloth.
The composition of your fabric really matters too. Unbleached cotton contains natural lignin that can absorb UV radiation. Shiny polyesters and even lightweight satiny silks can be highly protective because they reflect radiation. High-tech fabrics treated with chemical UV absorbers or dyes prevent some penetration from UV rays.
The more skin your outfit covers, the better your protection. Whenever possible, choose long-sleeved shirts and long pants or skirts.