Putting sunscreen on once in the morning is not enough. SPF wears off through sweat, water, towelling and simple rubbing, so reapplying is what actually keeps you protected through the day. But how often should you top up? Use the free sunscreen reapplication calculator below to get a clear answer based on what you are doing and the type of sunscreen you are using.
Sunscreen Reapplication Calculator
Find out when to reapply your SPF to stay protected.
General guidance. Always reapply after towelling, and use a generous amount (about a shot glass for the body).
How often should you reapply sunscreen?
As a general rule, reapply sunscreen every 2 hours when you are outdoors, and more often if you are swimming or sweating. Water-resistant sunscreens are only rated to keep working for 40 or 80 minutes in water, so once that time is up, or as soon as you towel off, you need a fresh layer. No sunscreen is fully waterproof or sweatproof, which is why topping up matters so much.
Why reapplying is so important
SPF is tested at a thick, even layer, but in real life the film breaks down. Sweat and water wash it away, clothing and towels rub it off, and UV light itself slowly degrades the filters. Skipping reapplication is one of the most common reasons people still burn even though they used sunscreen. Protecting your skin from UV also helps prevent premature ageing, dark spots and skin cancer.
How to apply sunscreen properly
Use enough: about a teaspoon for your face and neck, and roughly a shot glass (35–40 ml) for your whole body. Apply it 15 to 30 minutes before going outside so it can bind to the skin, and do not forget easy-to-miss spots like the ears, back of the neck, hairline and tops of the feet. Then reapply on the schedule above throughout the day.
Frequently asked questions
Do I need to reapply sunscreen if I stay indoors?
If you are away from windows, a single morning application is usually fine. But UVA rays pass through glass, so if you sit near a sunny window or drive a lot, reapply every couple of hours on exposed skin.
Does makeup with SPF count as sun protection?
It helps, but most people do not apply makeup thickly or evenly enough to reach the labelled SPF. Use a dedicated sunscreen underneath, and top up with an SPF powder or spray over makeup during the day.
Is a higher SPF better so I can skip reapplying?
No. A higher SPF gives a little more protection but still wears off. You should reapply on the same schedule no matter how high the SPF number is.