The SPF (sun protection factor) measures how well the sunscreen blocks out UVB rays—which are primarily what cause sunburns. The number tells you how long it would take to redden your skin versus the amount of time without it. For example, with SPF 15, it will take you 15 times longer to burn than if you were wearing nothing. So what number should you aim for?
Yes, tanning oil with SPF 8 technically is sunscreen, but it’s just not enough protection. The Skin Cancer Foundation recommends using broad-spectrum sunscreen with at least SPF 15. But should you go higher? Some say the often-pricier high-SPF sunscreens are a waste of money, since they don’t provide much more protection—SPF 30 blocks 97% of rays, while SPF 50 blocks just 1% more. However, they do have some benefit.
“They absorb more free radical-producing energy, so I recommend them for the summer,” Dr. Graf says. One caveat before you reach for the SPF 100: “The super-high SPFs can provide a false sense of security, like you’re protected for longer, but you need to reapply just as often as you would an SPF 30.”