SPF Facts: What Do The Numbers Mean?

When it comes to protecting yourself from the sun, it seems simple enough: the higher the SPF number on your sunscreen, the better. But have you ever wondered what those numbers actually mean? Or what SPF stands for? And what about E-SPF, or UPF?

Here are some facts about SPF to help you make sense of all those letters and numbers so you can protect yourself from the sun.

What Is SPF?
SPF stands for Sun Protection Factor. It's a measurement of how much sunburn-causing ultraviolet radiation reaches your skin. For example, if you are wearing SPF 30, only 1/30th of the UV rays that cause your skin to burn will penetrate your sunscreen. You can also use the SPF number to gauge the relative speed of your sunburn; if you're wearing SPF 15, it will take you 15 times as long to burn as it would if you were unprotected.

Of course, some types of ultra-violet radiation that cause skin damage do not cause sunburn and aren't blocked by conventional sunscreens, but in general, SPF is a simple way to determine how well protected your skin is from the sun.

Everyone knows that unprotected skin can be damaged by sun exposure, but did you know your eyes can be damaged by the sun too? Most sunglasses offer some UV protection by blocking UV from coming through the front side of the lens, but ordinary sunglasses don't offer protection from the UV rays reflected off the back side of the lens, which if reflected back into your eyes. So how can you tell which lenses offer UV protection on the front side and back side of the lens?

That's where the E-SPF® index comes in: E-SPF® is a global index rating the overall UV protection of a lens. E-SPF® was developed by Essilor International and endorsed by 3d party experts. A pair of sunglasses with an E-SPF® rating of 25 provides 25 times more UV protection than going without glasses, and some lenses such as Xperio UV can score as high as 50+ on the E-SPF® scale.

What About Your Clothes?
When it comes to protecting yourself from the sun, you probably don't think about your clothes too much. As long as you're wearing something, your skin is protected, right?

Actually, it turns out that different fabrics provide different levels of protection. Like SPF, UPF - Ultraviolet Protection Factor - measures the ratio of sunburn causing UV rays that penetrate fabric. Luckily, there are special types of sun protective clothing that provide UPF ratings of 30+.

So be sure to check the labels before going to the beach, because all those numbers can add up to a safer summer.