Every 40-80 minutes, depending on the label.

Reapply at least every 40 to 80 minutes if you’re swimming or sweating heavily—but check the bottle first. Sunscreens labeled “water resistant” are tested for either 40 or 80 minutes. That number is the max time before you need to reapply. If the label says 40, set a timer. If 80, you get a little more wiggle room.

Most people don’t reapply nearly enough. Water, toweling off, and sweat physically remove the sunscreen even if it feels like it’s still there. And if you use a spray? You’re probably missing spots. The FDA requires water resistance testing, but nothing accounts for how much you move or how much you wipe your face.

The real rule: after every swim, after every heavy sweat session, and definitely after drying off with a towel. If you’re outside all day, set an alarm. Sunburn is pain you don’t need to earn.

Honestly, just buy a sunscreen labeled “80-minute water resistant” and reapply every hour. Your skin won’t know the difference, but your future self will thank you.