Our Sunscreen Main Article provides a comprehensive look at the who, what, when and how of Sunscreen

Definition of Sun protection factor (SPF)

Sun protection factor (SPF): A number on a scale for rating the degree of protection provided by sunscreens. SPF stands for Sun Protection Factor.

SPF numbers on a package can range from as low as 2 to as high as 100. These numbers refer to the product's ability to screen or block out the sun's burning rays. It is a common mistake to assume that the duration of effectiveness of a sunscreen can be calculated simply by multiplying the SPF by the length of time it takes for him or her to suffer a burn without sunscreen, because the amount of sun exposure a person receives is dependent upon more than just the length of time spent in the sun. The amount of sun exposure depends upon a number of factors including the length of exposure, time of day, geographic location, and weather conditions.


Last Editorial Review: 6/14/2012

Search MedTerms:



Back to MedTerms online medical dictionary A-Z List
Pill Identifier Tool

Need help identifying pills and medications?
Use the pill finder tool on RxList.