Sunscreen Math: Can You Add Up SPF?

by Gio
Can you layer sunscreen and add up spf

Quick math question: what SPF do you get if you use a sunscreen with SPF 30, a moisturizer with SPF 20 and foundation with SPF 15?

30 + 20 + 15 = 30.

Huh?

In the words of Mona Gohara, a dermatologist and an associate clinical professor of dermatology at Yale University, “SPF isn’t an equation. Your sun protection is only as strong as your highest SPF.”

Here’s why:

Why Layering Sunscreens Doesn’t Increase Sun Protection…

Layering sunscreens will NOT give you added SPF protection. When you use several products with SPF, you end up only with the SPF of the highest sunscreen you applied.

You see, sunscreens work by limiting the number of UV rays that hit your skin. If you wear a SPF 20, for example, only 5% of UVA rays hit your skin. If you use SPF 50, 2% still get through.

So even if you use SPF 20 + SPF 50, you still get 2% of UV rays hitting your skin.

… But It May Still Gives You Better Sun Protection (When Done Right)

Layering products with SPFwill not add up SPF, but it may increase your overall coverage.

Let’s say you’re in a rush and applying sunscreen quickly. It’s easy to miss a spot or two. Those spots have no protection and are fair game for UV rays.

But if you slather on a second SPF product, you have more chances of covering every little nook and cranny. I personally don’t do this because I am very diligent with sunscreen application, but if you think you need it, go ahead.

Don’t Layer Mineral Sunscreens!

It’s easy to spot a mineral sunscreen. There are two mineral UV filters: titanium dioxide and zinc oxide.

I love them because they provide excellent protection without causing irritations. They’re so gentle, even babies can use them!

But – when they are uncoated – they don’t play with other synthetic filters like avobenzone and oxybenzone. They inactivate them so you get LESS sun protection.

FYI, in case you’re panicking because your sunscreen contains both titanum dioxide and avobenzone, relax. I said titanium dioxide inactivates avobenzone only when it’s uncoated. In a sunscreen that uses both, titanium dioxide is already coated.

But when you’re playing around with sunscreens at home, don’t take any chances. If you don’t know for sure if your mineral sunscreens are coated or not, layer them only with other mineral sunscreens.

Related: 3 Reasons Why Mineral Sunscreens Are Better For Sensitive Skin

The Bottom Line

SPF works by limiting the amount of UV rays that actually reach your skin. So adding up products with SPF won’t give you more protection. But it may give you better coverage.

Do you stick to sunscreen only or do you layer several products with SPF every day? Let me know in the comments below.

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12 comments

Socialite Dreams June 19, 2012 - 7:44 pm

most foundations and face creams have spf in them, so i end up mixing products with spf. works for me!

Reply
beautifulwithbrains June 19, 2012 - 8:58 pm

Socialite Dreams, that’s true. I guess because so many products contain SPF these days, we all tend to layer them, even if don’t do it on purpose. 🙂

Reply
Janessa June 20, 2012 - 3:08 am

I just stick to sunscreen though I have been using SPF moisturizer because I can get that into my hairline without it caking up and then I’ll blend some actual sunscreen into there and it works better (smoother application). Sometimes I use sunscreen for my brows (they’re a light black and taupe colors work best for filling them in) and sunblock for my face so that my brows don’t turn salt-and-pepper-grey on the days I don’t want to fill in my brows.
I have a question! I am in higher altitude and will be hiking up mountains to even higher elevations. I’m currently at 6035 ft or 1839meters above sea level lol… and it’s so dry here and it’s quite harsh on my already dry skin not to mention the literally scorching sun on my pale skin. I’ve been applying sunblock and touching up through the hot, slightly sweaty days (sorry if that’s gross) and I’ve brought my UPF 50 hat and wear long pants but what can I do? I’m just looking for advice. I really don’t want to burn lol. I burn with sunscreen (not sunblock) on.
<3 you are the person I trust and look up to!

Reply
beautifulwithbrains June 20, 2012 - 5:25 pm

Janessa, if you’re already applying sunscreen regularly and wearing protective clothing, I don’t think there’s anything more you can do unfortunately. If you still burn with the sunscreen you’re using, maybe you can try another one. The only other thing I can think of is to stay in the shade, but I know that’s not always possible.

Reply
Janessa June 20, 2012 - 6:29 pm

Okay, thank you so so much! You are the best! :] And I read your replies to other comments sometimes. You put all your heart into answering them! 😀

Reply
beautifulwithbrains June 21, 2012 - 8:42 am

You’re welcome. And aww thanks! 😳 I do my best to answer them as best I can.

Reply
Paris B June 20, 2012 - 6:17 am

This is a good post to think about. Many people think that by layering they can increase SPF coverage when nothing is further from the truth. I read somewhere once that the tip to bear in mind is that the highest SPF product you apply is the one that counts. The rest don’t. So I go with a high SPF sunscreen and I don’t mind or bother if other products (makeup/skincare) contain no SPF because I’m already protected 🙂

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beautifulwithbrains June 20, 2012 - 4:55 pm

Paris, that’s so true. Like you, I always use sunscreen too, so I don’t really mind whether the other skincare products I use contain SPF or not. I think that, while layering products may slightly increase your coverage (ie less chance to miss a spot), if you’re careful with application that shouldn’t be a problem anyway.

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xin June 20, 2012 - 8:28 am

i used to have the misconception of layering sunblock will have higher spf too! much later only i found out that i was wrong. i only use sunblock as my main spf, and top with powder sunblock for double protection

Reply
beautifulwithbrains June 20, 2012 - 4:51 pm

Xin, unfortunately most people think so and it’s a shame. Glad you’ve found out the truth and are using sunblock now instead than reliable solely on cosmetics.

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Pink January 30, 2015 - 6:33 am

I also heard that we shouldn’t mix products with SPF as they may interfere with each other and therefore give us less protection. So many sources and so many different opinions, it’s really hard to get some conclusion 🙁

Reply
Gio January 30, 2015 - 9:39 pm

Pink, that’s only partly true. Zinc oxide and titanium dioxide can degrade avobenzone, making it less effective. But that just means that you need to reapply the sunscreen more often. Or better yet, avoid using this combination. Hope this helps. 🙂

Reply

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