UPF 50+ Swimwear: What It Means and Why It Matters

The short answer: UPF (Ultraviolet Protection Factor) measures how much of the sun's UV radiation a fabric lets through. A UPF 50 fabric lets through only 1/50 of the UV rays, which means it blocks about 98%. UPF 50+ is the highest rating, described by the Skin Cancer Foundation as "excellent" protection.

UPF vs. SPF: what's the difference?

• SPF is for sunscreen. It measures protection against UVB, the rays that cause sunburn, and it wears off with water, sweat and toweling. The American Academy of Dermatology recommends reapplying at least every two hours, and right after swimming or heavy sweating.
• UPF is for fabric. It measures protection against both UVA and UVB rays, and it doesn't rub off, sweat off or need reapplying.

Sunscreen still matters for your face, neck and hands. But every inch of skin covered by UPF fabric is an inch you don't have to remember to protect.

Why sun protection matters

• Skin cancer is common. At least one in five Americans will develop skin cancer by age 70.
• Most of it is linked to the sun. About 90% of nonmelanoma skin cancers and about 86% of melanomas are associated with UV radiation from the sun.
• It shows on your skin. In fair-skinned women, an estimated 80% of visible skin aging, such as wrinkles and dark spots, is caused by the sun.
• Sun damage adds up. Only about 23% of lifetime sun exposure happens by age 18, so the protection you wear as an adult matters every day, not just on vacation.

What the numbers mean

• UPF 30–49: very good protection.
• UPF 50+: excellent protection. Only about 2% of UV rays get through.

The Skin Cancer Foundation only gives its Seal of Recommendation to fabrics rated UPF 50 or higher.

Why a T-shirt isn't enough

Many women swim in a regular T-shirt for sun protection. According to the Skin Cancer Foundation, a white T-shirt has a UPF of only about 7, and fabric that is wet or stretched lets even more UV through. That's exactly what happens to a T-shirt in the pool.

Three things decide how much protection a fabric gives:

• Color: darker and brighter colors absorb more UV than white or pastels.
• Weave: a tight, dense knit lets less light through.
• Fit: fabric stretched tight over the skin protects less than a relaxed fit.

Sun myths that catch swimmers

"It's cloudy, so I don't need protection."

Clouds block far less UV than most people think. Cool, overcast days can also make you stay outside longer, which is how people get burned without noticing.

"I'm in the water, so I'm cooler and safer."

Water keeps you cool, so you don't feel the sun burning. Meanwhile, UV reaches you from above and bounces back from around you: according to the World Health Organization, water reflects up to 10% of UV rays, sand about 15% and sea foam about 25%.

"I put on sunscreen this morning."

Swimming, sweating and drying off with a towel all remove sunscreen, and when you're having fun, it's easy to forget to reapply. Fabric protection stays in place the whole time you're wearing it.

"I only get sun on vacation."

Walking, swimming laps, watching the kids at the pool, gardening or biking: everyday moments add up. You don't have to be sunbathing to get a lot of UV exposure.

How HydroChic swimwear is protected

All HydroChic chlorine proof swimwear is made from fabric rated UPF 50+. The protection is built into the fabric itself, so it doesn't wash out. And because our chlorine proof fabric keeps its shape, it doesn't thin out and lose coverage after a season in the pool. Here's why chlorine proof matters.

"Very comfortable and fits well. Loved it also for the sun protection. Wore it on vacation and it was great."

— Denise C., on the Sport & Swim Athletic Zip Top

Where UPF 50+ swimwear makes the biggest difference

• Outdoor pools and water aerobics: an hour-long class in the midday sun adds up fast. See What to Wear to Water Aerobics.
• Beach days and cruises: sun reflects off water and sand. Browse our Cruise, Beach & Water Park Swimwear.
• Kids' swim lessons and family days: long hours on the pool deck, often without shade.
• Sun-sensitive skin: long sleeves and full-length bottoms cover the most skin. See Full Coverage Swimwear for Women.
• Reef-friendly swimming: the more skin your swimwear covers, the less sunscreen you need on your body and in the water. Hawaii, for example, has banned the sale of sunscreens containing oxybenzone and octinoxate since 2021 to protect its coral reefs.

Frequently asked questions

Does UPF protection wash out?

Not when it's built into the fabric, as it is in our swimwear. Some laundry-treated clothing loses protection over time, but fabric with UPF built into the fiber and knit keeps it.

Do I still need sunscreen with UPF 50+ swimwear?

Yes, on any skin the fabric doesn't cover, like your face, neck, hands and feet.

Is UPF 50+ swimwear hot?

Our fabric is lightweight and quick drying. Many women find a light layer more comfortable than baking in the sun with exposed skin.

Does UPF swimwear protect when it's wet?

Fabric designed for swimming is made to keep its protection in the water. That's the key difference from a cotton T-shirt, which loses much of its already low protection when wet.

Sources: Skin Cancer Foundation, Beyond Sunscreen: UPF Clothing Provides Excellent Sun Protection; Skin Cancer Foundation, Skin Cancer Facts & Statistics; American Academy of Dermatology and World Health Organization guidance, as reported by Consumer Reports; Hawaii state sunscreen law, in effect since January 1, 2021.