Does Cotton Have UPF? How Much UV Protection Does Cotton Provide?

Cotton can provide some protection from UV rays, but not all cotton clothing has a high enough UPF to provide reliable sun protection. A lightweight white cotton shirt may have a relatively low UPF, while a denser, darker, tightly constructed cotton fabric can provide considerably more protection. The only way to know how much protection a garment provides is to have the finished fabric tested.

UPF, or Ultraviolet Protection Factor, measures how much ultraviolet radiation passes through fabric and reaches your skin. Unlike SPF, which is used for sunscreen, UPF measures protection against both UVA and UVB radiation.

What do the different UPF ratings mean?

UPF ratings indicate the fraction of UV radiation that reaches your skin through the fabric:

For perspective, a UPF 15 fabric allows about 1/15 of UV radiation to pass through it. A UPF 50 fabric allows only 1/50 to pass through. TThink of it like a rain jacket in a downpour. UPF 30 is like a good rain jacket that keeps most of the rain out, while UPF 50+ is like an even more tightly sealed jacket—it lets less through. UPF 30 blocks about 97% of UV, while UPF 50+ blocks about 98% or more. The difference may seem small, but UPF 50+ allows less UV to reach your skin.

So, what is the UPF of cotton?

There isn't one UPF rating for cotton. Two cotton shirts can provide dramatically different levels of UV protection.

In one study published in the Journal of the American Academy of Dermatology, researchers tested two white cotton fabrics used for summer T-shirts. Their initial UPF values were just 4.94 and 3.13—far below the level generally considered adequate for sun-protective clothing. The researchers found that dyeing the fabrics and adding a UV-absorbing treatment substantially increased their UPF.

This is why “100% cotton” is not the same thing as “UPF 50.” Fiber content tells you what a fabric is made from; it does not tell you how much UV radiation the finished fabric blocks.

What makes cotton more protective?

Several characteristics affect the amount of UV radiation that can pass through cotton. Tighter construction, greater fabric density, increased weight, darker or more saturated colors, and certain dyes or UV-absorbing finishes can all increase UV protection. Conversely, lightweight, loosely woven or highly open fabrics tend to allow more UV radiation through.

The structure of the fabric matters because UV radiation can pass through the spaces between fibers. In fact, a study of summer clothing found that fabric cover—the amount of the surface actually occupied by fibers—was one of the most influential factors affecting UV protection.

What should you look for in a cotton sun-protective shirt?

If you're buying clothing specifically for sun protection, don't rely on the words cotton, thick, or long sleeve alone. Look for a garment with a tested UPF rating, ideally UPF 50+.

A UPF 50+ garment has been tested to allow less than 2% of UV radiation through the fabric. That's very different from assuming that an ordinary cotton shirt provides adequate protection simply because it covers your skin.

At Some Sun, our UPF 50+ fabrics are independently tested for UV protection so you don't have to guess how much protection you're getting from the fabric. The goal isn't simply to wear more clothing in the sun—it's to make the clothing you're already wearing work harder for your skin.

Sources: Wang et al., Journal of the American Academy of Dermatology; Davis et al., International Journal of Dermatology; Majumdar et al., Photodermatology, Photoimmunology & Photomedicine; Skin Cancer Foundation.