What the SPF Number Means A higher SPF doesn't indicate superior sun protection—it indicates that you will remain protected in the sun for a longer amount of time. For example, an SPF 2 product protects your skin just as effectively as one with an SPF of 30. However, SPF 2 sunscreen will need to be applied more frequently.
"SPF is not a consumer-friendly number," says Florida dermatologist James M. Spencer, MD. "It is logical for someone to think that an SPF of 30 is twice as good as an SPF of 15 and so on. But that ...
The "with sunscreen" number is divided by the "without sunscreen" number, and the result is rounded down to the nearest five. This is the SPF. SPF numbers start at 2 and have just recently reached 70. To figure out how long you can stay in the sun with a given SPF, use this equation:
An SPF 30 allows about 3 percent of UVB rays to hit your skin. An SPF of 50 allows about 2 percent of those rays through. That may seem like a small difference until you realize that the SPF 30 is allowing 50 percent more UV radiation onto your skin.
The American Academy of Dermatology recommends using a sunscreen that is SPF 30 or higher. Keep in mind, however, that although higher SPFs do mean more protection, the difference in that protection becomes smaller. SPF 15 = 93% UVB protection SPF 30 = 97% UVB protection
SPF, which stands for "sun protection factor," indicates how much sun exposure you're actually getting when you're outside. "SPF 15 protects against 93 percent of UVB rays, SPF 30 protects against...
SPF 15 blocks 93% of UVB rays, SPF 30 blocks 97%, and SPF 100 blocks 99%.
Rather, SPF is a relative measure of the amount of sunburn protection provided by sunscreens. It allows consumers to compare the level of sunburn protection provided by different sunscreens. For...
Experts recommend using a sunscreen with an SPF of at least 30. Sunscreens with SPF s greater than 50 provide only a small increase in UV protection. High-number SPF s last the same amount of time as low-number SPF s. Sunscreen is often not applied thoroughly or thickly enough, and it can be washed off during swimming or sweating.
SPF works by extending your skin’s natural defenses against the sun’s rays. For example, an SPF of 15 provides about 15 times more protection than just your normal skin without sunscreen. An SPF of...