The SPF number on a sunscreen label rates one thing: sunburn protection. The US Food and Drug Administration defines it plainly — "the SPF value indicates the level of sunburn protection provided by the sunscreen product." Whether that same bottle also filters UVA depends on a separate phrase, "Broad Spectrum," and on the product clearing a separate test.
That split is the single most useful thing to understand about a sunscreen label, because the two phrases do different regulatory work. SPF is a number produced by a sunburn test. Broad Spectrum is a pass/fail result. A high SPF with no Broad Spectrum designation is a legally accurate label describing a narrower product than most shoppers assume they are buying.
What does the SPF number actually measure?
SPF is a sunburn-protection factor, derived by comparing how much ultraviolet exposure it takes to redden skin with the product applied versus without it. The FDA's consumer guidance describes it in exactly those terms, and it ties the number to sunburn specifically rather than to overall sun damage.
Sunburn is driven largely by UVB radiation, which is why the SPF test on its own says nothing definitive about UVA. The federal labeling regulation at 21 CFR 201.327 reinforces this by restricting what a product can claim based on its SPF value and its broad spectrum status, not on SPF alone.
The number also assumes a laboratory application density that has little to do with how people apply sunscreen at the beach. The regulation's own directions section requires labels to tell users to "apply liberally 15 minutes before sun exposure" and to "reapply at least every 2 hours." Those instructions are part of how the SPF figure is meant to be delivered, not optional advice printed alongside it.
What does "Broad Spectrum" mean on a sunscreen label?
"Broad Spectrum" means the product passed a specific FDA test showing UVA protection proportional to its UVB protection. It is not a marketing adjective. According to the FDA's questions-and-answers page on its over-the-counter sunscreen requirements, only products labeled "Broad Spectrum SPF [value]" at SPF 15 or higher may claim to reduce the risk of skin cancer and early skin aging.
The regulation spells out the permitted wording. A qualifying product may state that "if used as directed with other sun protection measures (see Directions), decreases the risk of skin cancer and early skin aging caused by the sun," per 21 CFR 201.327.
Products that fail the broad spectrum test, or that test at SPF 2 through 14, must carry a warning instead. The required warning text in the federal regulation reads: "Skin Cancer/Skin Aging Alert: Spending time in the sun increases your risk of skin cancer and early skin aging. This product has been shown only to help prevent sunburn, not skin cancer or early skin aging." If you see that alert box, the label is telling you the product's claims stop at sunburn.
Why can't a sunscreen say "waterproof" or "sunblock"?
Because the FDA determined those words overstate what sunscreen does. Its over-the-counter sunscreen requirements bar manufacturers from labeling products "waterproof" or "sweatproof," and from calling them "sunblocks," on the grounds that the terms overstate effectiveness. Claims of protection lasting beyond two hours without reapplication, or of "instant protection," require FDA approval.
What replaced them is narrower and more testable. A label may state "Water Resistant (40 minutes)" or "Water Resistant (80 minutes)," and nothing in between or beyond, according to 21 CFR 201.327. The FDA notes that products without water resistance must direct consumers toward a water-resistant formula if they will be swimming.
The distinction matters at the register. Two bottles at the same SPF are not equivalent if one is rated to 80 minutes in water and the other carries no water-resistance statement at all.
How much sunscreen do you need to get the SPF on the label?
More than most people use. The FDA's consumer guidance is specific: "An average-sized adult or child needs at least one ounce of sunscreen (about the amount it takes to fill a shot glass) to evenly cover the body from head to toe." The agency also advises reapplying "at least every two hours, and more often if you're swimming or sweating."
The Centers for Disease Control and Prevention frames reapplication around behavior rather than the clock alone, advising in its sun safety guidance that you "put it on again if you stay out in the sun for more than 2 hours and after swimming, sweating, or toweling off." The CDC also recommends broad-spectrum sunscreen at SPF 15 or higher applied before going outside.
Two housekeeping details rarely make it into product copy. A sunscreen without a printed expiration date should be considered expired three years after purchase, per the FDA; the CDC gives the same three-year shelf life. And the FDA warns that while applying or wearing sunscreens labeled flammable, users should not smoke and should avoid open flames — a live consideration for aerosol sprays.
A label decoder for the phrases that carry legal weight
| Label phrase | What it means under FDA rules |
|---|---|
| SPF [number] | A sunburn-protection rating from a standardized test. It does not by itself address UVA. |
| Broad Spectrum | The product passed a test showing UVA protection proportional to its UVB protection. |
| Broad Spectrum SPF 15 or higher | Eligible to claim reduced risk of skin cancer and early skin aging when used as directed with other sun protection measures. |
| Skin Cancer/Skin Aging Alert | Required warning on products that are not broad spectrum or that test below SPF 15. |
| Water Resistant (40 minutes) or (80 minutes) | The only permitted water-resistance statements, tied to swimming or sweating time. |
| Waterproof, sweatproof, sunblock | Not permitted. The FDA considers these terms an overstatement of effectiveness. |
What could change on sunscreen labels next?
The FDA has proposed a set of revisions that would redraw parts of the label. In a fact sheet accompanying its 2021 proposed order on over-the-counter sunscreen, the agency states: "FDA is now proposing that the maximum labeled SPF value should be SPF 60+." The same document proposes "to require that all sunscreens with SPF values of 15 and above satisfy broad spectrum requirements."
That second proposal would close the gap this article opens with. If finalized, a high SPF number could no longer arrive without UVA protection attached.
The fact sheet also sorts active ingredients. Zinc oxide and titanium dioxide sit in the category the agency generally recognizes as safe and effective for sunscreen use. Twelve other filters — among them oxybenzone, avobenzone, octinoxate, octocrylene, homosalate and octisalate — fall into the category for which the FDA says additional data are needed. That is a request for evidence, not a safety finding, and the agency has not withdrawn those ingredients from the market.
None of this is final. A proposed order is a proposal, and the labels on shelves today still follow the existing requirements. Read the two phrases that already carry legal weight — the SPF number and Broad Spectrum — and the bottle will tell you what it has actually been tested to do.
For a related testing perspective, read How the SPF Number on Your Sunscreen Actually Gets Tested.