You apply sunscreen with an SPF of 30, head outside, and within 2 hours, your skin starts to turn pink. If this has ever happened to you, chances are you didn’t apply enough sunscreen. When the SPF of a sunscreen is determined, 2mg of the product is applied to each square centimeter of skin. However, day to day, people typically only apply about a third of this amount.¹ The warm weather has finally arrived, and whether you’re headed for a sunny vacation or gardening at home, wearing enough sunscreen is crucial.

So, how should you know how much sunscreen to apply to reach 2mg per square centimeter? A simple rule to follow is “one teaspoon per body part”, meaning one teaspoon per limb, another for your chest and abdomen, another for your back and the back of your neck, and one last teaspoon for your face, head, and the front of your neck.² While this rule can be handy, it isn’t accurate for everyone. The total amount of sunscreen needed to properly protect your skin depends on your body surface area, and how much skin you’re exposing to the sun. The Sun Index Sunscreen Calculator takes the guesswork out of applying sunscreen. It lets you know exactly how much sunscreen to apply based on your height, weight, and clothing choice.

The SPF rule is plain and simple: if you only apply a third of the recommended amount of sunscreen, you’ll only get a third of the marketed SPF.¹ Not applying the proper amount of sunscreen may give you the impression that your skin is more protected than it really is, putting you at risk of an unexpected sunburn. The next time you apply sunscreen, use the Sun Index Sunscreen Calculator to make sure you’re applying enough.

  1. Wang, S. Q. (2010). ASK THE EXPERT: Does a higher-SPF (sun protection factor) sunscreen always protect your skin better? Retrieved August 5, 2016
  2. Consumer Reports. (2015). How much sunscreen do I need? Retrieved August 5, 2016