A shot glass full for your body, a nickel-sized dollop for your face.

Pretty much everyone uses too little.

The SPF number on the bottle is tested at 2 mg per square centimeter of skin. That translates to about a full shot glass (roughly 1 ounce) to cover your whole body, and a nickel-sized blob (about a teaspoon) for just your face and neck. If you’re using a spray, you need to spray until it’s visibly wet and then rub it in — not a quick pass.

Most people apply half that or less, which means they’re getting SPF 15 from a bottle labeled SPF 30. That’s enough for a quick errand but not a day at the beach. Reapply every two hours or after swimming/sweating, because sunscreen breaks down.

Your future skin will thank you.