how long does sunscreen last?

i have high school which starts from 9:13-4. i put sunscreen on everyday SPF 50 and i was wondering how long it would last. 2 3 4 hours? and i was wondering if there was a sunscreen that stays on for 24 horus or something like that

I don't think there is one that lasts for 24 hours, but the fact is some sunscreens last for a short space of time, so the Sun Protection Factor is good but limited in duration, and you may need to apply it 2-3 times a day.

There might be some kind of consumer organisation or website, that does indpendant testing, that might be able to give you specific statistics for many well known brands, but I don't really know what else to say.

oh i see okay thx for the info boss man

i have high school which starts from 9:13-4. i put sunscreen on everyday SPF 50 and i was wondering how long it would last. 2 3 4 hours? and i was wondering if there was a sunscreen that stays on for 24 horus or something like that

I know sunscreen last 2 or 3 multiply the spf. so if it's 50 multiply by 2 or 3, that's how long it could stay...

I've read studies that say that after SPF 30 or 35, the protection doesn't change as you go up...eg SPF 30 is as effective as SPF 50. But...there's a study that proves both sides of every argument, so whatever.

Nothing will be effective for 24 hours. You're suppose to reapply every 2-3 hours or after a swim or a good sweat (especially if you towel off). It says so on the back of the sunscreen bottle.