UPF stands for Ultraviolet Protection Factor, which is a measurement of the sun protection strength of clothing and fabrics used in outdoor shades (e.g. umbrellas, shade sails, pavilions, awnings and screened-in porches). It represents the ratio of UV radiation exposure with and without the protection of the measured textile.
What does UPF mean?
There are many factors that go into the calculation of UPF ratings, but at the end of the day you probably just want to understand what the numbers indicate. You might want to know, “what is UPF 50?” In this example, a fabric with UPF 50 will permit only 1/50th (2%) of ultraviolet radiation to pass through it.
What is a good UPF rating?
Obviously, the higher the UPF the stronger the protection against the sun. However, there are levels of protection that you should be aware of as you evaluate textiles for patio umbrellas, shades and outdoor clothing [Bilimis 2011].
Levels of UPF Protection
|UVR Protection||UPF Rating||UVR %|
|Moderate||10 to 19||10 to 5.1|
|High||20 to 29||5.0 to 3.4|
|Very High||30 to 49||3.3 to 2.0|
What’s the difference between SPF and UPF?
SPF stands for Sun Protection Factor, which is used to measure the effectiveness of sunscreen and other products. It is a time-related measurement relative to your skin’s natural tendency to burn. A sunscreen with an SPF rating of 30 provides 30 times more protection against UVB rays than if you wore no sunscreen at all. So, if you have fair skin and tend to burn after 10 minutes, applying SPF 30 sunscreen will allow you to be exposed for up to 300 minutes without burning. As mentioned above, UPF measures the UVA and UVB radiation that penetrates a textile and reaches the skin.
What’s the difference between UVA and UVB radiation?
- UVA rays account for nearly 95% of the ultraviolet radiation that reaches the earth’s surface. They penetrate deep into the skin’s dermis and over time can lead to premature aging of the skin, cause wrinkles and suppress the immune system. Recent studies have shown that UVA rays also damage skin cells in the lower layer of the epidermis, where most skin cancers develop. These rays can penetrate cloud cover and glass.
- UVB rays are more intense, but far less prevalent than UVA rays. They are the primary cause of skin reddening, sunburn and other superficial damage to the skin’s outer epidermal layer (e.g. tanning, photo-aging, etc). UVB radiation plays a significant role in the onset of skin cancer. These rays do not penetrate glass to any measurable degree, but they do bounce off of reflective surfaces, so they can burn you when you are under cover or during icy winter months.
What characteristics affect a fabric’s UPF?
This is an important question to answer because we all have preconceived notions about what is appropriate to wear during the summer. Lightweight white see-through fabric shirts may allow a breeze to cool your skin in the heat, but are they really the best sun protective clothing to wear? UPF clothing and patio umbrella canopies are more than just their aesthetics.
- Weave – The tighter the fabric is woven together, the less UV radiation passes through
- Color – Dark colors of identical fabric types absorb ultraviolet rays more strongly than their lighter shades, which increases the sun protection
- Weight – A heavier version of the same fabric will be minimally more protective against UVR
- Stretch – The greater the stretch or tension put on a textile, the lower the UPF rating
- Water – Some fabrics, such as polyester and cotton, provide less protection against UVR when they have absorbed water
- Washing – Cotton-based fabrics tend to shrink after the first washing, thereby tightening the weave and reducing the transmitted ultraviolet radiation
- Additives – UVR stabilizers or additives can be used to improve the sun protection of a variety of textiles
[Gies, Roy, Toomey, & McLennan 1998]
Frequently Asked Questions – UPF
UPF is short for Ultraviolet Protection Factor. It's a numerical sun protection rating given to fabrics used for patio umbrellas and clothing. The UPF number is the ratio of ultraviolet (UV) radiation protection with the measured textile versus without. So, a fabric with UPF 50 allows only 1/50 of the UV radiation through.
Rating Levels of UPF Protection (% UV rays allow through) 10 to 19 - Moderate (10 to 5.1%) 20 to 29 - High (5.0 to 3.4%) 30 to 49 - Very High (3.3 to 2.0%) 50+ - Maximum (<2.0%)
UPF vs SPF While UPF measures the UV protective strength of fabrics, SPF or Sun Protection Factor rates sunscreen effectiveness. It measures the relative tendency of your skin to burn using a sunscreen versus not wearing any at all. For example, if you tend to burn after 10 minutes, a sunscreen with an SPF rating of 50 will enable you to stay in the sun for up to 500 minutes without burning (i.e. 50 times more protection than no sunscreen at all).
It's difficult to say which is better because UPF and SPF measure different things and actually work together to protect your skin (covered up and exposed) from harmful ultraviolet radiation from the sun. The Ultraviolet Protection Factor measures the effectiveness of your clothing or shade at stopping UV rays from reaching your skin, while the Sun Protection Factor rates a sunscreen's ability to extend the time you can be in the sun without burning.
All other characteristics being equal, fabrics that are darker or more vivid in color absorb UV radiation more than lighter or paler ones. The more a fabric absorbs ultraviolet rays, the more sun protection it provides. A bright yellow patio umbrella canopy is more protective than a pale one.
- Bilimis, Z. (2011). Measuring the UV protection factor (UPF) of fabrics and clothing.
- Gies, P. H., Roy, C. R., Toomey, S., & McLennan, A. (1998). Protection against solar ultraviolet radiation. Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis, 422(1), 15-22.
- Soter, N. A. (2017). Acute effects of ultraviolet radiation on the skin. In Clinical Photomedicine (pp. 75-93). Routledge.