You’ll find this on your bottle or tube of sunscreen, and may have wondered what it stood for along with the associated number. SPF is an abbreviation for Sun Protection Factor, and the number associated with it is known as the amount of time measured for the sunscreen’s effectiveness.
So if you are using an SPF of 15, it would protect you for approximately 150 minutes depending on a number of variables. These range from SPF’s of 15 to 45, 90+ and 100+. It is highly recommended that you apply at least SPF 15 at 2 hour intervals and that you should apply as much as one ounce to your entire body.
The American Cancer Society states that SPF ratings do not however offer 100% protection from the sun, but rather SPF 15 protects you from 93% of harmful UVB rays, SPF 30 protects you from 97%, while SPF 50 protects you from up to 98% of the UVB rays.
For the highest amount of protection, it is best to use a broad spectrum or full-spectrum sunscreen that protects your skin from both UVA and UVB rays. Older sunscreen formulations only protected the skin against UVB rays, while UVA rays could still penetrate deeper into the skin causing long term damage unnoticeable to the naked eye. More recent sunscreen formulas such as broad spectrum SPF protect skin from both.
Defined in Australia in 1996, UPF is an abbreviation of Ultraviolet Protection Factor and is used to measure the sun protection clothing can offer from powerful sun rays. Much like broad spectrum sunscreen, UPF protects the skin from both UVA and UVB rays by absorbing or reflecting light.
UPF ratings are equivalent to SPF ratings, and so, UPF of 30 would provide the same protection as SPF sunscreen of 30, absorbing up to 97% of the rays. Comprehensive testing goes into determining the UPF rating of clothing items, and then assigned the UVBlock™ official certification under the International UV Testing Laboratories.
UPF ratings determine the amount of UV radiation the fabric can absorb before reaching the skin. Heavy dark cotton fabric like denim for example usually carries a UPF rating of up to 50 – making it an ideal long sleeve clothing item when outdoors for prolonged periods.