Sunscreen Calculator
Choose which parts of your body are exposed and how long you will be outdoors. The calculator gives the amount of sunscreen for each application, how many applications you need, and the total for the day.
Free, no sign-up. What you enter stays in your browser: it is not saved or sent to HerFound. Reviewed .
Which skin is exposed?
Pick every area that clothing will not cover, or whole body for swimwear.
Swimming or sweating?
Bottle size in
Enter it to see how many days like this one the bottle covers.
Pick the areas of skin that will be exposed to see how much sunscreen to use.
This is general information, not medical advice. It cannot take your own health history into account. For anything that worries you, speak to a doctor, midwife or pharmacist.
How it works
Amounts follow the teaspoon rule for adults: one teaspoon (5 ml) for the face, neck and ears, one for each arm, one for each leg, one for the front of the torso and one for the back. That adds up to 7 teaspoons, or 35 ml, for the whole body. The rule exists to reach 2 mg of sunscreen per square centimetre of skin, which is the amount used when a product's SPF is tested.
These figures sit close to the advice from health bodies. The American Academy of Dermatology says most adults need about 1 ounce, roughly a shot glass, to cover the body, and at least 1 teaspoon for the face. The NHS says around 6 to 8 teaspoons for the whole body.
Applications are counted as one before you go out, then one every 2 hours: the number of hours divided by 2, rounded up. If you will swim or sweat, one extra application is added, because sunscreen should go back on straight after water, sweating or towelling, even if the label says water resistant.
Total for the day = amount per application × number of applications. If you enter a bottle size, days per bottle = bottle size ÷ total for the day. Fluid ounces are converted at 29.57 ml per US fl oz.
What it cannot tell you
- The amounts are for an average adult. A larger body needs more, and the calculator does not adjust for your size. It is not designed for children.
- It does not change your SPF or tell you how long you can stay in the sun. No sunscreen blocks all UV, and the American Academy of Dermatology says a high SPF lasts no longer than a low one.
- Sunscreen is one part of sun protection. Shade and clothing matter as much, and the NHS says not to rely on sunscreen alone.
- Babies under 6 months should be kept out of direct sunlight; the NHS does not recommend sunscreen for them. See a doctor about a mole or patch of skin that changes in size, shape or colour.
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Common questions
Use at least 1 teaspoon of sunscreen for your face, which is about 5 ml. The American Academy of Dermatology describes this as the amount that covers the length of your index and middle fingers. Under the teaspoon rule that amount also covers the neck and ears.
An adult needs about 35 ml of sunscreen to cover the whole body, which is 7 teaspoons. The American Academy of Dermatology puts it at about 1 ounce, roughly a shot glass, as a minimum, and the NHS says around 6 to 8 teaspoons. Most people apply much less than this.
Reapply sunscreen every 2 hours when you are outdoors. Put it on again straight after swimming, sweating or drying yourself with a towel, even if the product is labelled water resistant. This is the advice of both the NHS and the American Academy of Dermatology.
A 200 ml bottle of sunscreen covers an adult's whole body fewer than 6 times, at 35 ml per application. On a full day at the beach with three applications, that is about two days for one person. A bottle used only on the face, at 5 ml a time, lasts far longer.
No. A higher SPF does not mean you can use less sunscreen or reapply less often. The SPF on the label is measured with 2 mg of product per square centimetre of skin, so a thinner layer gives less protection than the label says.