3 Things You Might Not Know About Your Sunscreen (That You Should)

updated May 3, 2019
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(Image credit: Shyvoronkova Kateryna)

Do your summer plans include a little fun in the sun? Don’t forget the sunscreen! And don’t forget these three facts about your sunblock, either. A lot of people don’t know that a sunblock’s real SPF – sun protection factor – changes from person to person, or that the SPF labeled on the bottle can be wildly inaccurate.

There’s a Little (Easy) Math to Find Your SPF

SPF stands for sun protection factor, and to find out exactly how protected you’ll be, you’ll have to do a simple calculation. Take the amount of time, in minutes, it takes your unprotected skin to burn (2 minutes? 10? 30?) and multiply that number by the SPF number on the bottle to find out exactly how long you’re protected. For example, when a person who normally takes 10 minutes to burn applies 30 SPF sunscreen, their safe sun duration will be 300 minutes (or 5 hours) until they begin to get a sunburn. But…

Shocker: SPF Isn’t Always Accurate

Consumer Reports tested more than 60 sunscreen lotions, sprays and sticks that all claimed an SPF of 30 or higher. But they found that 28 of them (43%) did not meet their advertised SPF levels. Three of them had an SPF of less than 15. The lesson here is always to under-estimate your sun protection. If your math from the SPF formula tells you you’re safe for 5 hours, you’d better re-apply after 2.

Why You Should Take a Shot Glass to the Beach

One to two ounces is the recommended amount of sunscreen needed to coat the average person’s body. That’s a shot glass full. Sound like a lot? It does to a lot of us; most people only apply half or less of the recommended amount of product. So use a heavy hand when you coat up and you can relax knowing you’re completely protected while you lounge on the sand.