Sun protection
Is the SPF in my moisturizer or makeup enough?
Rarely. The SPF number assumes a thick layer, about a quarter teaspoon for the face; moisturizer and foundation go on thinner and miss the eyelids. Fine for a mostly indoor day; outdoors, use a real sunscreen.
- Tested amountAbout a quarter teaspoon for the face
- Real useA quarter to a half of that, eyelids missed
- Under makeupA proper sunscreen first on any real-sun day
On this pageWhat the SPF number assumes4
Quick answer
The bottom line
An SPF number is measured with a thick, even layer of product, about 2 milligrams on every square centimetre of skin, which for a face is roughly a quarter teaspoon. Nobody applies foundation or a light day cream at that thickness, and studies of how people really apply sun protection find they use between a quarter and a half of the tested amount, which turns an SPF 30 into something closer to single digits. A study that photographed people under ultraviolet light found SPF moisturizer users also missed more of their face than sunscreen users, especially around the eyes. For a day mostly indoors, an SPF moisturizer is a reasonable baseline. For commuting, lunch outside, driving or any real sun, apply a dedicated sunscreen at the proper amount under your makeup, and reapply if you stay out.
At a glance
Three things worth remembering
- Under ultraviolet photography, SPF moisturizer users missed more of their face than sunscreen users, especially around the eyes.[3]
Section 01
What the SPF number assumes
SPF is measured in a laboratory by applying 2 milligrams of product to every square centimetre of skin, a layer that feels heavy and looks white for a moment, and measuring how much longer that skin takes to redden. That is the dose the number belongs to; FDA guidance and dermatology guidance both describe it. For the face and neck it works out to about a quarter teaspoon, or a strip of product along two fingers.[2][1]
A review of how people actually apply sun protection found typical use at a quarter to a half of that amount. Protection does not fall in proportion; it falls faster, so an SPF 30 applied at half thickness gives something in the region of SPF 5 to 10. A tinted moisturizer or foundation is applied thinner still, because a quarter teaspoon of foundation would look like a mask.[4]
Section 02
The coverage problem
Thickness is one problem; where it goes is another. A study photographed volunteers under ultraviolet light after they applied either an SPF moisturizer or a sunscreen as they normally would. The moisturizer group left more of the face uncovered, and both groups missed the eyelids and the area around the eyes most, which is where a large share of skin cancers on the face occur.[3]
Foundation is worse again because it is applied where you want colour, blended thin at the hairline, jaw and around the eyes, and rarely on the ears or neck. The product may carry a real SPF; the way it is used does not.[3][1]
Section 03
When it is enough
A day spent mostly indoors, with a short walk and windows, is low exposure, and an SPF moisturizer applied generously is a reasonable baseline for it. NHS guidance treats sunscreen as one part of sun safety alongside shade and clothing and is clearest that protection matters when ultraviolet is strong, which in most places means late morning to mid-afternoon in the sunnier months.[5]
Layering two thin SPF products does not add up: SPF 15 moisturizer under SPF 20 foundation gives you roughly the better of the two, not 35. If your day includes real sun, treat the makeup SPF as a bonus and put a sunscreen underneath.[1][4]
Section 04
How to get real protection under makeup
Apply a broad-spectrum sunscreen of SPF 30 or higher as the last skincare step, at the full quarter-teaspoon amount, including eyelids, ears, hairline and neck; let it settle for a few minutes; then apply makeup as usual. Choose a sunscreen texture you like, because the one you will wear at the right amount beats a better one you thin out. Dermatology guidance suggests a mineral or lightweight fluid for makeup wearers.[1][2]
Outdoors, sunscreen needs reapplying about every two hours. Over makeup, an SPF powder or spray is convenient but goes on thin, so use it generously, and count on a hat and shade to do the rest. On a beach or hiking day, makeup with SPF is not part of the plan at all.[1][5]
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