As summer approaches, many consumers face a familiar dilemma at the sunscreen aisle: SPF 30, 50 or even 100? The numbers are ubiquitous on product labels, but what they actually mean for skin protection can be more complicated than they appear.
Two board-certified dermatologists spoke with PolitiFact to address common questions about sun protection factor ratings and how consumers can make informed choices this summer.
What the Left Is Saying
Public health advocates and progressive health policy organizations have long emphasized the importance of broad sunscreen education, particularly for communities that historically received less messaging about sun safety. The Skin Cancer Foundation, a nonprofit focused on skin cancer prevention, has advocated for clearer labeling standards to help consumers understand SPF ratings.
"People deserve clear, accurate information about what they're putting on their bodies," the foundation stated in recent consumer guidance. "The difference between SPF 30 and SPF 50 is marginal, but both provide meaningful protection when applied correctly."
Dermatologists who work with diverse patient populations note that skin cancer education has sometimes overlooked communities with darker skin tones, though research shows sun protection remains important for all skin types.
"Lower SPF sunscreens may feel lighter or be easier to wear, but they provide less protection," said Dr. Adewole Adamson, a dermatologist and internal medicine professor at the University of Texas at Austin. "The higher the number, the more margin of error you may have if you under apply."
What the Right Is Saying
Free-market advocates and some consumer groups have raised questions about regulatory overreach in sunscreen labeling requirements, arguing that adults should be able to make informed choices without excessive government guidance.
"At what point does health policy become paternalism?" asked a commentary from a free-market think tank focused on consumer freedom. "Adults can read labels and consult their doctors."
Some conservative commentators have also pushed back against what they characterize as excessive sun safety messaging, arguing that moderate sun exposure has documented health benefits including vitamin D production.
Dr. Marisa Garshick, a dermatologist based in New York and clinical dermatology professor at New York Presbyterian-Weill Cornell Medicine, noted that higher SPF sunscreens can sometimes create a false sense of security among users.
"Someone wearing SPF 100 may think they can stay in the sun significantly longer without reapplying, which is not the case," Garshick said. "Whether you're reaching for SPF 50 or SPF 80, it's important to use enough sunscreen and reapply frequently."
What the Numbers Show
According to the U.S. Food and Drug Administration, SPF measures how much solar energy it takes to burn skin with sunscreen compared to the solar energy needed to burn skin without sunscreen.
SPF 30 filters approximately 97% of UVB rays, while SPF 50 filters approximately 98%, according to dermatologists cited in the report. SPF 100 filters about 99% of the sun's UVB rays.
The FDA banned the term "sunblock" in 2011 because no sunscreen can block all UVB rays.
Key protection statistics: SPF 30 blocks roughly 97% of UVB radiation; SPF 50 blocks approximately 98%; SPF 100 blocks about 99%. The incremental gain in protection decreases as numbers increase, while higher-SPF products often cost more, according to UC Davis Health.
Peak UV hours occur between 10 a.m. and 4 p.m., when sun exposure poses the greatest risk, according to dermatological guidance.
The Bottom Line
Dermatologists recommend using at least SPF 30 sunscreen labeled "broad spectrum," which protects against both UVA and UVB rays. For water activities or sweating, consumers should select products also labeled "water resistant."
Regardless of SPF rating, experts emphasize reapplication at least every two hours or immediately after swimming, water activities, or heavy perspiration.
The protection difference between SPF levels is modest once applied correctly. Higher SPF does provide more margin for error if sunscreen is not applied as generously as recommended, but no product offers complete UV protection.