SPF 50 isn't twice as protective as SPF 30.

Not as much as you’d think.

The math is misleading. SPF 30 blocks about 97% of UVB rays. SPF 50 blocks about 98%. That’s a 1% difference in a lab. In real life, people don’t apply enough sunscreen, don’t reapply, and sweat or rub it off. So that 1% theoretical edge gets swallowed up by human error.

The real practical difference: SPF 50 gives you a slightly longer buffer before you need to reapply. But if you’re only using half the recommended amount—which is most of us—your SPF 30 might be giving you SPF 15 anyway. Focus on using enough (about a shot glass for your body) and reapplying every two hours. That makes way more difference than the number on the bottle.

Pick a sunscreen you’ll actually use and reapply—that matters more than the SPF number.