The Comparison, in One Table
| SPF 30 | SPF 50 | |
|---|---|---|
| UVB blocked | About 97%, per the American Academy of Dermatology | More — but at most the last 3% |
| Meets dermatologist advice (SPF 30+) | Yes | Yes |
| Best for | Everyday wear and most skin | Long outdoor days and sun-sensitive skin |
| Still needs | Broad spectrum, enough product, reapplying | Broad spectrum, enough product, reapplying |
What the Number Actually Means
According to the FDA, SPF indicates the level of sunburn protection a sunscreen gives, and because it comes from a test that measures sunburn, it primarily reflects protection against UVB. Protection against UVA comes from the words broad spectrum, not from the number. Higher SPF values, up to 50, do provide greater sunburn protection.
The FDA also warns against a common misreading: SPF is not a timer. A higher number does not mean you can multiply the time you spend in the sun, and every sunscreen still needs reapplying at least every two hours, and more often if you are swimming or sweating.
Which to Choose
- Everyday, mostly indoors: a broad-spectrum SPF 30 is enough — see daily face sunscreens.
- Long outdoor days, the beach or high altitude: SPF 50 with water resistance, reapplied — see body sunscreens.
- Very fair or sun-sensitive skin, or using acids and retinoids: lean toward SPF 50.
- Whichever you choose: the one you will actually apply generously, every day.
The American Academy of Dermatology recommends a sunscreen that is broad spectrum, SPF 30 or higher and water resistant. Water resistance lasts either 40 or 80 minutes, so check the label before swimming. For filter types, see chemical vs mineral sunscreen.
