What Is UPF Clothing?

Ultraviolet protection factor, or UPF, ratings are to fabrics what sun protection factor (SPF) ratings are to sunscreen: They indicate what fraction of the sun’s ultraviolet rays can penetrate a given fabric. A UPF rating of 25, for example, means the material allows 1/25 (4 percent) of UV radiation in, and a UPF 50 garment lets in 1/50 (2 percent).

Frustrations with sunscreen—the need for frequent application, the inevitable greasy feeling, and the potential risk to aquatic life—along with an increased awareness of the hazards of extended sun exposure, have helped expand the UPF-clothing industry from mostly utilitarian pieces to a wider variety of appealing, everyday styles. You can now find UPF clothing from dozens of companies and in thousands of designs, all using tighter weaves or treated fabrics (or often, both) to better block the sun’s rays. Some brands (such as Coolibar, Mott50, and UV Skinz) specialize in UPF clothing, while other labels (from Lilly Pulitzer to Uniqlo to Athleta) now offer UPF pieces as well. Wirecutter has reviewed some UPF clothing and accessories, including surfing rash guards and sun hats for adults, plus swimsuits, rash guards, and sun hats for kids.

Like sunscreen, UPF clothing goes through testing at independent labs—but unlike with sunscreen, that testing is completely voluntary rather than a regulatory requirement. Companies that make and sell UPF fabrics in the US typically adhere to complementary standards set by ASTM International (formerly the American Society for Testing and Materials) and the American Association of Textile Chemists and Colorists (AATCC). Clothing tags often state a UPF rating, but not necessarily whether companies have complied with those specific standards. A Seal of Recommendation from the Skin Cancer Foundation does indicate compliance, though not all brands apply for this distinction.

Some UV radiation passes directly to the skin through micro-spaces between the fibers of most fabrics, some is absorbed by the fibers, and some is scattered off by reflection. Labs use the ASTM and AATCC protocols to measure how much of this radiation gets through specific fabrics. Moisture can also affect a fabric’s UPF: Dry garments are generally more protective than those same pieces once they are wet.

A garment isn’t considered sun protective if it has a UPF rating lower than 15, and to earn the Skin Cancer Foundation’s Seal of Recommendation, a voluntary recognition, it must have a rating of at least 30 from one of those independent bodies. According to Dr. Adele D. Haimovic, a Skin Cancer Foundation spokesperson, UPF 30 or higher offers sufficient protection, but “50+” offers the best available. (Likewise, although any sunscreen technically offers some skin protection, the American Academy of Dermatologists recommends SPF 30 and above.) A UPF value above 50 doesn’t provide significantly improved protection, so instead of reporting UPF 100, or UPF 500, which sounds impressive but means nothing, most brands simply report 50+.

Of course, some non-UPF-rated clothing—including garments you likely already own—can protect you from the sun, too. You “don’t need to buy UPF clothing for all the time,” Haimovic said.

If you’re looking to dress with sun safety in mind, here are a few general qualities to consider:

• The tightness of the fabric’s weave: As you might expect, “a tightly-woven piece with smaller holes between the thread, like denim, will offer more protection than one with an open weave, like a crocheted shawl,” Haimovic explained.
• Color and thickness of the fabric: Thicker, darker fabrics are more protective than thin, light ones. “A bleached cotton offers little protection, whereas a black corduroy would block more UV radiation,” said Haimovic. A lightweight, 100 percent cotton white T-shirt has a UPF of around 5.
• Material composition: Synthetic materials are better at protecting against UV radiation than natural ones. Generally speaking, polyesters and rayons outperform wools and cottons.
• Material fit: If a garment stretches against your skin, there will be larger gaps in the fibers, and more light (and radiation) will reach you. Looser fits offer more protection (and more breathability, too).
• Coverage: Of course, whether your garment is UPF-rated or not, the more skin it covers, the more skin it can protect. (Think longer sleeves, wider brims, and the like.)

Covering yourself head to toe in denim would be highly protective, but unless you love to sweat or profoundly believe in the sartorial appeal of a Canadian tuxedo, it’s likely impractical for spending a lot of time in the sun because that material also traps heat and moisture. For covering up comfortably, UPF-rated clothing is typically lighter and more breathable, and—especially with that Skin Cancer Foundation seal—offers guaranteed protection.