How much sunscreen you actually need
The SPF on the label is measured at 2 mg per square centimetre. Apply thinner than that and the real protection drops with it. Pick the areas you cover, and see how many grams that is, how many fingertips, and how long one tube lasts.
What if you apply less than that
This is where most people fall short. Studies find that people typically apply only 25–50% of the standard amount. Move through the options below to see roughly what protection is left at the amount you really use.
These figures are an estimate for an average adult build. They are worked out from 2 mg per square centimetre, the amount SPF is tested at internationally, with skin area approximated using the Rule of Nines. Real amounts vary with body size, product texture and how you apply it. Use this to plan roughly, and always read the label and directions of the product you are using.