How Much Sunscreen Do You Really Need For Your Body?

As a beauty editor, I can't say or write these three words enough: Put on sunscreen . And not just during the summer months when it's scorching hot, but every single day.

Okay, so now that I've drilled that beauty rule into your head, you're probably wondering exactly how much sunscreen do you really need. And yes, the amount does matter, according to cosmetic dermatologist Dr. Dina Strachan , who gave us a refresher on summer skincare at a Escape with Hawaiian Tropic event.

"The 1 ounce shot glass or golf ball-sized amount is a reference point -- likely for the 70 kg (155 lb) man," explains Dr. Strachan. "If one is smaller or larger, then more or less sunscreen need be applied to achieve the SPF listed on the bottle."

If you don't have a shot glass lying around, you can never go wrong by smoothing on way more sunscreen . Just be sure that you apply the product to all exposed areas evenly. "If one is in continuous sun," says Dr. Strachan, "the sunscreen should be applied every two hours and after heavy sweating or getting wet."

While the face deserves the most attention, Dr. Strachan believes that "people often forget to also protect the scalp, ears, neck and upper chest in strong sun."

This derm's final words of advice when it comes to protecting your skin from harmful UVA and UVB rays ? Look out for the SPF number (which means sun protection factor or the factor by which protection is increased with proper use of the product).

"The American Academy of Dermatology recommends that people use an SPF of at least 30 on both the face and body," says Dr. Strachan. "Although an SPF of 15 is adequate, in reality most people don't use enough product to achieve it. With a higher SPF, it is believed that the recommended minimum of 15 will be achieved based on usage."

The more you know ...