What do the numbers mean?
Your sunscreen's Sun Protection Factor indicates the level of protection it affords against sunburn. The numbers make it easier for people to choose the sunscreen best suited to their complexions and conditions of exposure.
In broad terms, you can say that an SPF
of 10 or under is Low
between 10 and 20 is Medium
between 20 and 40 is High
over 40 is Very High
Use sunscreen for protection, not to stay out longer in the sun!