When it comes to getting the most out of your sunscreen dollars, they don't come more authoritative than Doctor Louis Kuchnir. He is the president of the Massachusetts Academy of Dermatology and a dermatologist practicing in Milford, Massachusetts.
"Each of us is so different in terms of how vulnerable we are to say sunburns or even skin cancers. The amount that you need to use needs to be personalized," Doctor Kuchnir explained.
That said, one way a lot of people are wasting a lot of money, Doctor Kuchnir says, is by paying big premiums for sunscreen rated SPF 50 or 80 or even 100.
"15 is probably fine for everyday sunscreen use. For going to the beach, even at a northern latitude like here, a 30 is probably appropriate. You certainly could burn through a 30 but that's easier to do in Florida or the Caribbean.
According to the Skin Cancer Foundation, SPF 15 sunscreen will block out 93 percent of UVB radiation. SPF 30 will block out 97 percent and SPF 50 will block out 98 percent. That's why it's important to understand what SPF is and isn't.
"If ten minutes of sun would cause a burn, and with sunscreen you can 300 minutes of the same amount of sun before burning, that sunscreen has a SPF of thirty. It's simply a ratio of how long it takes to burn with the sunscreen versus without," Doctor Kuchnir explained.
So unless you're super sun-sensitive or lying on a beach for eight hours at a time, paying for more than SPF 30 may well be a waste of money.
Experts also recommend applying sunblock 30 minutes before sun exposure and to re-apply every two hours and after swimming.