SPF stands for sun protection factor. You’ll see this written on sunscreens in numbers like 15, 30, 50, and even 60+. SPF is a guide to how a sunscreen will help prevent sunburn. It is important to remember that regardless of the SPF number, you should be reapplying sunscreen every 2 hours, and more frequently if you are swimming or sweating.
While the FDA recommends choosing a broad-spectrum sunscreen with an SPF of at least SPF 154, SPF 15 stops up to 93% of UVB rays, whereas SPF 30 stops up to 97%, and SPF 50 up to 98%5. No matter how high an SPF number goes, there is no SPF that can stop 100% of the sun’s harmful rays. After SPF 50, higher SPF numbers provide marginally higher protection.
To help protect your face from visible signs of premature aging from the sun, choose a high face SPF and be sure to reapply regularly, following directions on the packaging.