Do you need SPF 30, 50 or 100? Dermatologists answer your burning sunscreen questions

By — Madison Czopek, PolitiFact Madison Czopek, PolitiFact Leave your feedback Share Copy URL https://www.pbs.org/newshour/health/do-you-need-spf-30-50-or-100-dermatologists-answer-your-burning-sunscreen-questions Email Facebook Twitter LinkedIn Pinterest Tumblr Share on Facebook Share on Twitter Do you need SPF 30, 50 or 100? Dermatologists answer your burning sunscreen questions Health May 30, 2026 6:15 PM EDT This article originally appeared on PolitiFact The numbers that signal summer's approach are here: The countdown to the last day of school. A 90-degree forecast. And, of course, SPF 30. Or 50? Or maybe it's time to break out SPF 100? SPF stands for sun protection factor. That sounds simple enough, but what these ubiquitous figures mean in practice can be complicated. We asked two board-certified dermatologists to answer our burning SPF questions. What do different SPF numbers actually mean? READ MORE: Why it's important everyone wears sunscreen — even if you have a darker skin tone The numbers tell you how well a sunscreen protects your skin against ultraviolet B, or UVB, rays — the type of ultraviolet radiation most responsible for causing sunburns. The higher the SPF, the more these UVB rays are blocked, said Dr. Adewole Adamson, a dermatologist and internal medicine professor at the University of Texas at Austin. Doubling the SPF doesn't mean the sunscreen protects twice as well, however. SPF 30 sunscreen filters about 97% of UVB rays, for example, and SPF 50 filters about 98%, said Dr. Marisa Garshick, a dermatologist based in New York and clinical dermatology professor at New York Presbyterian-Weill Cornell Medicine. You can think of SPF as a measure of how much solar energy it takes to burn skin with sunscreen compared to the solar energy needed to burn skin without sunscreen, according to the U.S. Food and Drug Administration . What SPF is high enough? Use at least SPF 30, but even higher is better. That's partly because most people don't apply enough sunscreen, which means they get less protection than what the label advertises. "Lower SPF sunscreens may feel lighter or be easier to wear, but they provide less protection," Adamson said. "The higher the number, the more margin of error you may have if you under apply." What else should I look for when selecting sunscreen? Buy sunscreen with a "broad spectrum" label, which means it protects against UVA and UVB rays, dermatologists said. SPF can tell you only how well a sunscreen blocks UVB rays, not ultraviolet A or UVA rays that are also harmful. Much like UVB rays, UVA rays have been linked to sunburns, wrinkles and some skin cancers. READ MORE: Why do skiers sunburn so easily? A snow scientist explains If you'll be sweating or spending time in the water, you should use sunscreen that is also labeled "water resistant." "Most of all, find a sunscreen that feels good on your skin because sunscreen will only work if you use it," Adamson said. Does SPF 100 block 100% of UVB rays? No.