How much sunscreen should I pack for a beach trip?

Work out how many bottles you need

Multiply the number of adults by the number of full beach days, then multiply by 4 ounces. Divide that total by the ounces in each bottle to get your bottle count, rounding up when necessary. A bottle shared by four adults is shared stock, not four bottles in disguise. These examples use 4 ounce bottles and do not include extra sunscreen for additional swimming breaks.3

How much goes on each time?

Most adults need at least about 1 ounce per application to cover skin not covered by clothing, roughly a shot glass full. Larger bodies can need more. Another practical measure is around 6 to 8 teaspoons for the entire body. These are approximate coverage guides, not a reason to stop applying before every exposed area is covered. Applying a thinner layer reduces protection, so stretch your supply by packing enough rather than rationing each application.24

For your face, use at least 1 teaspoon. Cover your neck, ears, tops of your feet and exposed scalp too, and pack an SPF 30 or higher lip balm. Clothing changes how much skin needs sunscreen, so a trip spent mostly covered up is different from several days in swimwear. The adult estimate is not a fixed dose for children: cover all their exposed skin, including ears, feet and backs of hands.245

Count reapplications, not just mornings

1. 1Apply generously to dry, exposed skin before leaving. Allow 30 minutes before going outdoors; NHS advice for prolonged exposure also calls for another application just before you go out.
2. 2Reapply about every 2 hours while outdoors. Include enough sunscreen for those repeat applications when calculating your supply.
3. 3Reapply straight after swimming, sweating or towel drying, and whenever sunscreen has rubbed off. Follow the bottle's water resistance directions while swimming rather than waiting for the usual 2 hour interval.

What should the bottle say?

Choose broad spectrum protection, meaning protection against both UVA and UVB rays, and a water resistant formula. SPF 30 is the minimum; SPF 50 or higher is a sensible choice for extended outdoor activities such as a beach day. A higher SPF does not let you use less sunscreen or wait longer between applications. For sensitive skin, look for mineral filters such as zinc oxide or titanium dioxide.14

Check whether water resistance lasts 40 or 80 minutes. Neither means waterproof, and you still need to reapply after toweling off. Read the actual water resistance time rather than choosing by the product name.6

Pack protection beyond the bottle

Check expiry dates before packing, and keep sunscreen accessible in a cool place. Avoid leaving bottles in direct sunlight or a hot car, because heat can spoil sunscreen. Pack protective clothing, a broad brimmed hat and UV protective sunglasses as well. Use shade alongside those measures: sunscreen alone does not provide complete protection, and sand and water reflect the sun's rays.3457