U.S. Sunscreen Labels: What SPF and Claims Mean

Sunscreen labels can look like a row of competing promises, but in the United States each key claim has a specific job. SPF describes a product’s tested protection against sunburn; “Broad Spectrum” signals that it also meets a separate test for UVA protection; and a water-resistance statement gives a tested time under water-related conditions. According to the U.S. Food and Drug Administration (FDA), none of these claims means a sunscreen blocks every ray or lets people ignore the rest of the label.

What SPF and “Broad Spectrum” measure

SPF stands for sun protection factor. FDA’s SPF test compares the ultraviolet (UV) exposure that produces sunburn on protected skin with the exposure that produces sunburn on unprotected skin, under a standardized test. The resulting number is chiefly a measure of protection against UVB, the part of UV radiation that causes most sunburn; it is not a clock. An SPF 30 label does not mean a person can stay in the sun 30 times longer. Exposure varies with conditions, and sunscreen wears or rubs off.

The number also is not a simple percentage scale. The American Academy of Dermatology (AAD) explains that, under test conditions, SPF 15 filters about 93% of UVB rays and SPF 30 about 97%; neither filters 100%. The jump from 15 to 30 therefore adds protection, but not a doubling of the share filtered. These figures are useful comparisons, not a promise of the same result on every person or in every situation.

“Broad Spectrum” answers a different question: whether the product also passes FDA’s test for UVA protection. According to the U.S. sunscreen regulation, the test measures absorption across UVA and UVB wavelengths, with a critical wavelength of at least 370 nanometers required for the claim. On a U.S. package, a product that passes can show “Broad Spectrum SPF [number].” Broad Spectrum is not an SPF multiplier or a claim of complete UVA blocking; it indicates that the product met this defined test.

That distinction matters when a package makes broader health claims. Under the regulation, only a sunscreen labeled Broad Spectrum with SPF 15 or higher may state that, when used as directed with other sun-protection measures, it decreases the risk of skin cancer and early skin aging caused by the sun. FDA says products that do not qualify must carry a warning that they have been shown only to help prevent sunburn. The label claim is bounded; it is not a guarantee against sun damage.

Water resistance, timing and the test’s limits

“Waterproof” and “sweatproof” are not permitted U.S. sunscreen claims because they overstate how long protection lasts. A qualifying front label instead states “Water Resistant (40 minutes)” or “Water Resistant (80 minutes).” FDA’s test guidance describes cycles of immersion in water and drying, followed by the SPF test; the listed time indicates that the product retained its tested SPF through those immersion conditions. It does not mean the sunscreen cannot wash off, or that it remains unchanged through every swim, towel rub or workout.

Reapplication language is part of the Drug Facts directions, not optional fine print. For a water-resistant product, the regulation says the label directs users to reapply after 40 or 80 minutes of swimming or sweating, as applicable, immediately after towel drying, and at least every two hours. For a product without a water-resistance claim, directions say to reapply at least every two hours and use a water-resistant sunscreen if swimming or sweating. The FDA consumer page likewise says to reapply at least every two hours and more often after swimming or sweating; the product’s own directions specify the tested interval.

Tests are controlled comparisons, not a simulation of every day outside. FDA’s SPF method applies a standardized amount—2 milligrams per square centimeter—to test sites before UV exposure, while people’s real-world application and circumstances can differ. The broad-spectrum test is performed on prepared plates in a laboratory, rather than measuring a personal outcome. The tests establish whether a product meets specific claim criteria; they do not predict exactly how long a particular person will avoid sunburn or establish total protection under all conditions.

For a dry walk or commute, the practical label-reading move is to compare the SPF and check whether “Broad Spectrum” appears, then follow that bottle’s Directions. For a beach day, pool session or sweaty outdoor activity, check for the exact water-resistance duration and its matching reapplication instructions rather than relying on words such as “sport.” As the Centers for Disease Control and Prevention (CDC) puts it, sunscreen works best alongside other protection, including clothing and shade.

This explainer covers U.S. sunscreen labels and FDA rules. Other countries use different testing systems and label terms, so a U.S. claim should not be assumed to mean exactly the same thing elsewhere. The most reliable reading is the full local label: what was tested, what the claim says, and when the directions say to reapply. For a separate U.S. sunscreen development, see GenZ NewZ’s report on a new sunscreen ingredient reaching shelves after a quarter century.