How much sunscreen do you really need to apply?

We put this question to a skin doctor and the answer might surprise you. 


Recently, a colleague of ours went to the Caribbean-island of Bonaire armed with a bottle of Rituals sunscreen (of course). Within three days the bottle was empty and he had to go in search of SPF, which he found at an eyewatering price. And our colleague is not alone, according to one study by The Hospital Group 67% of people don’t apply enough sunscreen.  


So, we decided to put the question to an expert: How much sunscreen do you really need to apply? We called on aesthetic doctor, Dr. Sophie Shotter to explain, once and for all, how much sunscreen we should be using on our face and body, as well as how often we should reapply. Why is this important? Preventing skin burning is crucial, not just because getting sunburnt is painful but because Cancer Research UK notes that ‘getting sunburnt just once every two years can triple your risk of melanoma skin cancer, compared to never being burnt.’ Time to slather on that sunscreen...

How much sunscreen for the face 

Our face is often exposed to the sun. Of course, we can wear hats and sunglasses when we’re out and about and on vacation but if you work in an office with windows (and the office dress code doesn’t include hat and sunnies) UV rays can penetrate the glass and your complexion so opt for a high factor like 50.  


When it comes to the amount you should apply, Dr. Shotter says, “the face alone needs 2 finger lengths of sunscreen to provide adequate coverage.” Use less and you won’t be benefitting from “the full SPF value and UVA rating of the product,” she adds. 


And keep in mind that this amount is just for the face and neck, you need that same amount again for your chest.  


How much sunscreen for the body 

For an adult body you should imagine using one full shot glass of sunscreen as a bare minimum. This will obviously vary according to body surface area,” says Dr. Sophie Shotter, but it’s a guide. “For children, think about using around half a shot glass full for each child. 


“When thinking about how much to apply to each body area, a good rule of thumb is that each leg, the head and neck, the abdomen, the chest, the upper back and the lower back are each 9% of body surface area. Whilst each arm is 4.5%. Broken down this looks like: 



Around 10% of your total quantity, or 2 fingers of a dedicated face sunscreen for adults. 



About 10% of your total quantity.  


Torso and abdomen 

Also around 10%. 



To cover the whole upper and lower back you need around 20%, that’s 4 fingers of sunscreen. 



About 10% of the total, so 1 finger of sunscreen per arm and hand. 



About 10% of the total to each leg and foot, so around 2 fingers of sunscreen per leg and foot. 


Of course, this doesn’t equal to the full 100% because if you’re on a beach holiday, for example, more than likely parts of your body will be covered by swimwear. But be sure to apply extra at the edges of your swimwear and your hairline, as these spots can easily be missed leading to unexpected sunburn.  


At Rituals, our sunscreen for body is a milky spray formula, so we asked Dr. Sophie Shotter whether this affects the amount needed? “I would still use the same guidance, although obviously it can be harder to get a visual quantification for a milky spray. You need to think about getting your skin looking like it’s glistening which can give a good guide.” 


Shop The Ritual of Karma sun care here.

Why you need to apply sunscreen before going in the sun 

It’s no myth that you should apply your sunscreen before going out in the sun. According to the American Academy of Dermatology, “it takes approximately 15 minutes for your skin to absorb the sunscreen and protect you. If you wait until you are in the sun to apply sunscreen, your skin is unprotected and can burn.” 


How often you should reapply sunscreen 

When it comes to reapplying sunscreen, Dr. Sophie Shotters says it should be “at a minimum, every 2 hours. You should also reapply after intense exercise where you’ve sweated or whenever you’ve been in water. If you’re in a hot country with strong sunshine I would recommend reapplying every hour.” 


Top tip: When it comes to reapplying over makeup, you can use a makeup sponge to tap it over your foundation and top with powder to take down any unwanted shine.  


How much sunscreen to take on vacation 

Not sure how many bottles of sunscreen to take with you on holiday? This handy sunscreen calculator works it out based on your size, length of vacation and the duration each day that you’re planning to be in the sun.  

Amy Lawrenson

Amy Lawrenson

Amy Lawrenson is a UK beauty editor with over 13 years of experience writing for magazines and websites including ELLE, Grazia, Women's Health and Byrdie. She has a keen interest in all things beauty and wellness, especially skincare because who doesn't want a clear, glowing complexion?