What Is the Difference Between SPF 30 and SPF 50?

Higher SPF ratings generally mean better protection from the sun's ultraviolet B rays, so SPF 30 sunscreens provide protection from 97 percent of UVB rays and SPF 45 or higher sunscreens block 98 percent. The SPF rating, however, does not signify how much protection someone gets from ultraviolet A rays, which are also linked to skin cancer, according to the Skin Cancer Foundation.