How to Choose Sun-Protective Hiking Clothes - Backpacker

Oct 16, 2024

Hiking in Moab Photo: Cavan Images via Getty

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If you’re an avid outdoors person, you likely gave up on sunscreen after your first backpacking trip. That sticky mess is a nightmare when a future shower isn’t guaranteed, or when you have reapply after every intense ascent or skinny-dip. That’s why—for most backpackers—sun-protective hiking clothes like sun shirts, pants, and hats are the way to go.

Outdoor apparel promises sun-blocking potential with a value called Ultraviolet Protection Factor, or UPF. An actual rating is better than just guessing at sun protection, but it also opens a whole can of worms about the rating system. Does the number really matter? How high do I need to go? Here’s everything you need to know to buy your next sun layer.

In short, UPF is a way to measure the amount of protection an article of clothing provides from UV rays. It’s a quantitative measurement of the percentage of ultraviolet radiation (UVR) that passes through a fabric. A UPF 50 rating means that the garment allows 1/50 of all UVR to pass through the fabric, while a UPF 15-rated garment would allow 1/15. In other words, UPF 15, 30, and 50 ratings block 93.3 percent, 96.6 percent, and 98 percent of UVR, respectively.

Although this sounds a lot like the SPF rating used in sunscreen, UPF and SPF ratings are different.

SPF is a measure of how long it takes unprotected skin to burn compared to skin covered in sunscreen. In theory, wearing SPF 15 sunscreen means it would take 15 times as much sun exposure to cause a sunburn.

In a perfect environment, SPF and UPF are equal (that is, a SPF 15 sunscreen and a UPF 15 shirt would offer equal protection). But because of all the variance in sunscreens (like how much sunscreen you apply, how long it lasts, and how often you reapply) the Food and Drug Administration says that SPF is nothing more than a “relative measure of the amount of sunburn protection provided by sunscreens.” In other words, SPF 30 sunscreen will be more effective than SPF 15, but there’s no guarantee of how long it will last or how likely you are to burn after using it. UPF ratings are far more consistent. As long as the fabric is covering your skin, its rating shouldn’t change much.

There are a lot of factors that relate to a fabric’s UPF rating. Here are the big ones.

If your goal is the best protection possible, it might be tempting to make sure all of your summer apparel is rated UPF 50+. But is that actually necessary?

There isn’t broad consensus as to what UPF rating is “good enough.” According to the US standard, UPF 15 is considered “good” sun protection, while the European standard only considers UPF 40+ to be sun protective. The Skin Cancer Foundation recommends clothing with UPF 30+, and says that “excellent” protection starts at UPF 50. One study that links UPF ratings to UV indexes concluded that UPF rating should be 4.13 times higher than the maximum UV index for the best protection. As I’m writing this, the UV index today at my home in Boise will max at 10.2 (very high), giving me a recommended UPF rating of 42.1.