Researchers at Consumer Reports have a warning for us, though: nearly half of sunscreen products in the U.S. fail to live up to the SPF claim on their bottles.
The group independently evaluated the SPF (Sun Protection Factor) value of 65 sunscreen products, including lotions, sprays, and sticks, and found that 43% of them had less SPF than their label promised.
If you’re like me, and no amount of SPF ever seems to be enough anyway, you could go home looking like a lobster. Do that enough, and you could wind up with skin cancer.
The American Academy of Dermatology recommends choosing a sunscreen that is at least 30 SPF, which would block 97% of UVB rays.
Patricia Calvo, Consumer Reports’ deputy content editor for health and food, who worked with the researchers to create the report, told CNN:
“[Sunscreens] should live up to the claim on their label, and in our test we found some of them did not.”
In fact, over the past 4 years, since the FDA updated requirements for how sunscreen manufacturers label and test their products, 48% of sunscreens have failed to live up to their promises.
The worst offenders: Banana Boat Kids Tear-Free, Sting-Free Lotion and CVS brand Kids Sun Lotion. Both were labeled as 50 SPF, but were found to have only 8 SPF.
Mineral products, commonly called “natural” sunscreens – most of them containing only titanium dioxide, zinc oxide, or both as active ingredients – were especially terrible. A mere 26% of the 19 mineral sunscreens tested met their SPF claims. 
Trisha Calvo, Consumer Reports’ deputy content editor of health and food, told “CBS This Morning” Tuesday:
“What’s interesting about those sunscreens is that they are the ones that contain titanium dioxide and zinc oxide is the active ingredients. Those mineral-based sunscreens overall in our test didn’t perform as well as the ones with chemicals like avobenzone.”
And if you’re looking for a waterproof sunscreen, forget it; Consumer Reports says “no such product exists.” Shiseido’s WefForce Ultimate Sun Protection Lotion SPF 50+ recommends soaking in water for 30 minutes before application, to “enhance” the products protective capabilities. The researchers found that wasn’t entirely true.
The magazine tested it on both dry skin and on skin that had been soaked for the recommended amount of time. Calvo said:
“…we found no difference in the SPF performance, but I have to say that the sunscreen met its SPF claim and it provided excellent UVB protection.”
Consumer Reports says your best bet is to apply sunscreen 15 minutes before you go outside, and reapply every 2 hours, “no matter what sunscreen you’re using.” There’s not a huge difference in protection between SPF 50 and SPF 100; it’s all in the chemical content (unfortunately). But if you want SPF 30 protection, apply an SPF 40 sunscreen, just in case the product you’re using doesn’t live up to its claims.
Choose lotions over sprays, too. Calvo explained:
“You have to be careful with spray because you can inhale them and it’s also hard to get a complete coverage. You don’t get the protection if you don’t… use enough, if you don’t reapply often enough.”
Consumer Reports says sprays should only be used as a “last resort.” 
Not that you need visual proof of that last recommendation, but a Reddit user posted this photo with the following caption:
“My friends first time in the Florida sun. Apparently it was also their first time using spray on sunscreen.”
 CBS News