UPF hiking pants: what the rating means and when it matters

What the number means

The Skin Cancer Foundation defines UPF, Ultraviolet Protection Factor, as how much UVB and UVA radiation a fabric allows to reach your skin. A UPF 50 fabric lets two percent, one fiftieth, through and blocks 98 percent. It rates UPF 30 to 49 as very good and UPF 50+ as excellent, and a fabric needs UPF 50 to qualify for its Seal of Recommendation. [1]

The arithmetic is simple: transmitted UV is 1 divided by the UPF. That makes the jump from UPF 30 to UPF 50 smaller than it sounds in absolute terms but still meaningful on long days.

What changes protection on the trail

The rating is measured on fabric; what you wear on a hike is fabric under conditions. The Skin Cancer Foundation lists the factors: dark or bright colours absorb UV, densely woven cloth protects more than sheer or loosely woven cloth, tight clothing can stretch and lose protection, and clothing that gets stretched or wet loses some protective ability. More skin covered means better protection. [1]

The CDC makes matching points: wear long sleeves and long pants when possible, tightly woven fabric offers the best protection, a wet T-shirt protects less than a dry one, and darker colours may protect more than lighter ones. [2]

• Stretch: a snug pant over bent knees protects less than the same fabric relaxed.
• Wet: sweat or a stream crossing reduces protection.
• Colour: darker or brighter colours absorb more UV, which conflicts with light colours recommended for spotting ticks; choose based on the bigger risk on that trail.
• Coverage: unzipped convertible legs remove protection from the lower leg entirely.

Pants versus sunscreen

The Skin Cancer Foundation notes that UPF covers both UVB and UVA, while SPF measures only UVB, and that unlike sunscreen you never need to reapply clothing. [1] The CDC recommends broad-spectrum sunscreen of SPF 15 or higher and putting it on again if you stay in the sun more than 2 hours and after swimming, sweating or toweling off. [2] On a six-hour exposed hike, long pants remove the need to reapply on your legs at least twice, which is a practical advantage even before the rating is considered.

When a UPF rating actually matters

For a shaded forest hike, any long pant covers your legs and the rating is a minor factor. For desert, alpine, beach or open-ridge hikes over a couple of hours, a stated UPF of 30 or higher gives you a known baseline rather than guessing from weave and colour. Not every hiking pant states one: Moosehill's HikerFlex M015 page, for instance, lists fabric and a water-repellent finish but no UPF rating. [3] An unrated pant is not necessarily poor protection; it is simply unverified.

Checklist for reading a UPF claim

Treat a UPF number as a seller claim until the listing gives enough detail to check it.

• Is a specific number stated, such as UPF 50, rather than vague sun-protective wording?
• Does the page say whether the rating applies to the whole garment or only certain panels?
• Does the listing name a test method or certification? If not, ask the seller.
• Will you wear the pant stretched tight or often wet? Expect less protection than the label.
• For long exposed days, pair the pants with sunscreen on any skin still uncovered.

Sources & verification

Product details and prices can change. Check the linked provider before buying.

1. The Skin Cancer Foundation: Sun-Protective Clothing Accessed 30 Oct 2026
2. CDC: Sun Safety Facts Accessed 30 Oct 2026
3. Moosehill HikerFlex M015 men's convertible hiking pants product page Accessed 30 Oct 2026