UPF 50+ is all you need.

Yes. After that, it’s about comfort, fit, and durability — not marketing hype.

UV protection in clothing is measured by UPF (Ultraviolet Protection Factor). UPF 50 blocks 98% of UV radiation, which is the best rating you’ll commonly find. Anything labelled UPF 30 or 40 is fine, but why settle for less when 50 is widely available and not more expensive? Ignore “blocking 99% of UVA/UVB” claims — that’s just UPF 50 rephrased.

The real differentiator is fabric and construction. Look for a tight weave (stretch it slightly — if you see gaps between threads when stretched, it’ll let more UV through). Nylon-spandex blends are common, durable, and dry quickly. Polyester-spandex works too but can feel less breathable. Avoid cotton rash guards; they get heavy when wet and lose UPF rating when soaked.

Fit matters more than you’d think. A loose rash guard lets light sneak in through gaps at the collar, sleeves, and hem. It also flaps around in the water, which is annoying. Get one that’s snug but not compression-level tight unless you’re training. Check that the neckline covers your collarbone area (a common burn spot) and that sleeves reach your wrist when you reach overhead.

Brands don’t matter much at this level. The same factories in China and Vietnam make most of them. Spend $25–40 on Amazon or a surf shop; the $80 versions last longer only if the seams are reinforced and the fabric is heavier. For occasional beach use, the cheap ones hold up fine for a season or two.

Just check the tag for UPF 50. That’s the only keyword you need.