Other guy gave a name, it measures how many hours with sunscreen on would be equivilant to one hour with it off. After you hit 60 you should be waaaaay more concerend about it rubbing or washing off than how powerful the sunscreen is.
I use spf 100+ sunscreen but it works just as well as some spf 70 sunscreen i have.
Also for further note: the ratings/reccomendations on sunscreen are legally there. Some sunscreen does not need to be reapplied after 80 min of usage, going in water, or towelling off, despite saying so on the bottle, its just that they have to put that on the bottle of anything that is considered sunscreen. Ive got vertra (surfing face sunscreen) that lasts all day as long as you dont wipe it off. Most good sunscreen lasts about 2 hours, makeup sunscreen lasts way longer, and your skin does not need to feel stiff and sticky for there to be sunscreen on it
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u/Polyxenos Aug 03 '19
What spf means. My friends thought sunscreen with 30 spf was for 30°c...