What level of SPF (Sun Protection Factor) do I need?

A product’s Sun Protection Factor (SPF) is defined as the ratio of the least amount of UVB energy required to produce a minimum erythema (redness) reaction after sunscreen application, as compared to the amount of energy required to produce the same reaction without using a sunscreen. For instance, if it takes you 10 minutes to develop redness after sun exposure and you apply a sunscreen with an SPF of 15, theoretically you should be protected approximately 15 times your 10 minute exposure or about 150 minutes before you might develop the same level of skin redness. Many factors influence the SPF effectiveness of a sunscreen product, including your skin type, when the product is applied, the quantity and uniformity of the application, and the time of day you are out-of-doors.

Depending on your skin type, there are different levels of SPF that should be used. For the very fair complexion, which burns easily and doesn't tan, use SPF 20 to 30. For the fair complexion, which burns easily and tans minimally, use SPF 12 to 20. For light skin, which burns moderately and tans gradually, use SPF 8 to 12. For medium skin, which burns minimally and always tans well, use SPF 4 to 8. For dark skin, which rarely burns and tans profusely, use SPF 2 to 4.