What is UPF Ultraviolet Protection Factor on apparel?  Many customers inquire about the specifics of UPF ratings on court apparel that we stock.  Having forgotten the details and aware that technology continues to evolve with fabrics utilized in athletic wear, I thought I’d freshen up on my UPF IQ and share what I’ve found.

What is UPF?

UPF is essentially built-in sunscreen for clothes.  The UPF rating is the fraction of UV rays that can pass through the fabric and is based on the content, weight, finish and color of a particular fabric.  A UPF of 50 means that 1/50th, or 2% of the sun’s rays will hit the skin.  All clothing provides some degree of UPF naturally.  For instance, it is said that most standard white t-shirts provide a UPF rating of about 7.

Who says so?

In order for apparel manufacturers to (legally) advertise its UPF rating, it has to be ASTM certified either using the U.S.A. or international standards.

How does UPF get into / onto the clothes?

Fabric companies sometimes work sunscreen ingredients into the fibers, and / or use a tighter weave in making these particular fabrics.  Early on, this tended to rely more on a coating of the material, however today’s UPF rated fabrics tend to be engineered with a tighter weave to accomplish the task.  This way it won’t wash off over time.  The tighter the weave, the fewer holes that sun can penetrate.  The more reflective the fabric (shinier rather than a matte finish), the more the UV rays will reflect off rather than absorb into it.  The thicker (or heavier) the fabric the more protection it will usually afford as well.

Quick Tips

  • Lycra, Nylon and Polyester fabrics tend to provide the most UPF protection
  • If you are a fan of cotton, wash your garment to preshrink it before wearing in the sun to close the gaps in the weave 
  • Don’t wear a shirt so tight that you are stretching it and opening the weave
  • Seek a garment of at least 30 UPF for a fair amount of protection

Have tips for us? Please share!