SPF

Also known as: Sun Protection Factor, Broad-Spectrum

Sun Protection Factor. Measures UVB protection only. Broad-spectrum covers UVA and UVB. SPF 30 blocks ~97% of UVB; SPF 50 blocks ~98%. No sunscreen blocks 100%. Apply 2mg/cm² (about a shot glass for the body) and reapply every 2 hours outdoors.