How much sunscreen should I use? Calculator
Almost everyone applies a quarter to a half of the amount sunscreen is tested at, which turns SPF 50 into roughly SPF 10 to 20. Pick what you are covering and get the real amount, plus how long your bottle should last if you are using enough.
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See what daily SPF does to your skin over time
Sun exposure shows up as uneven tone and lost radiance long before wrinkles. Gloss tracks clarity and radiance from a daily selfie, so you can watch them improve once the SPF habit sticks.
Cosmetic tracking only, not medical advice. Your scan photo is analyzed and discarded, never stored.
Why the amount matters more than the SPF number
SPF is measured in a lab at 2 milligrams of product per square centimetre of skin. Studies of real people find most apply between 0.5 and 1 mg per cm². Protection does not scale in a straight line, so applying half the amount gives you far less than half the SPF. SPF 50 at half thickness behaves closer to SPF 7 to 15. Buying a higher number does not fix this. Applying enough does.
The quick references
- Face: two finger lengths, or a quarter teaspoon, or about 1 g.
- Face, neck and chest: about half a teaspoon, roughly 2 g.
- Whole body in swimwear: a full shot glass, about 30 g, per application.
- A 50 ml face sunscreen: should run out in roughly 6 to 8 weeks of daily use on face and neck. If yours lasts six months, you are using a quarter of the tested amount.
Two layers is a legitimate trick
Two thin layers a minute apart are easier to spread evenly than one thick one, and end up at the same total. Missed patches (around the hairline, the sides of the nose, the ears) are the other big loss, and a second pass catches them.
Reapplication
Every two hours in direct sun, and after swimming, sweating or towelling off. On an indoor day near windows one good morning application holds up reasonably well, and a top-up at lunch is a good habit. Powder and spray top-ups over makeup are better than nothing but rarely reach the tested thickness.
Common questions
How much sunscreen should I put on my face?
About 1 gram, which is two finger lengths of cream or a quarter of a teaspoon. Add another finger length for the neck and another for the chest.
How many fingers of sunscreen for face and neck?
Three to four finger lengths total: two for the face, one to two for the neck and upper chest.
How long should a 50 ml bottle of face sunscreen last?
Six to eight weeks if you apply the tested amount to your face and neck once a day. Longer than that means you are under-applying.
Is SPF 50 much better than SPF 30?
At full application, SPF 30 blocks about 97% of UVB and SPF 50 about 98%. The bigger difference in real life is that most people under-apply, and a higher SPF gives you more margin for that.
How often should I reapply sunscreen?
Every two hours in direct sun, and immediately after swimming, heavy sweating or drying off with a towel.
Gloss and the tools on this site are for cosmetic and general information only. They do not diagnose or treat any condition. If something on your skin is new, changing, painful or worrying, see a dermatologist or doctor.
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