Medically reviewed by Mary Lucas, MSCIS, MPhil, RN
Written by Our Editorial Team
Last updated 11/18/2021
How does SPF even work? It’s a question some people learn from a very young age, and others learn much later, or when problems begin.
We obsess about chemical sunscreens and mineral sunscreens and spend significant amounts of time wondering if there's a particular facial sunscreen best for acne-prone skin or a darker skin tone.
We pick sunscreens with high SPF numbers for dry skin or oily skin types, all in hopes that the words on the bottle means less sun damage and more ultraviolet light protection, while we sit awkwardly by the pool covered in white residue and zinc oxide.
Meanwhile, our friends become golden, slathered in coconut oil.
So what is to be done for basic, non-pool day protection? Surely we don't need those big SPF 70 formulas for UVB protection, right?
The right daily protection for your casual sun exposure isn't a riddle. You just need to understand SPF to know the answer.
We can get the easiest things about SPF out of the way quickly.
SPF stands for Sun Protection Factor. It’s a numeric scale used for grading the “blocking power” of a sunscreen lotion or other product.
As you’ve probably always assumed, a higher number means higher protection levels. The higher the number, the better the protection.
More specifically, the Food and Drug Administration defines it as, “a measure of how much solar energy (UV radiation) is required to produce sunburn on protected skin.”
Basically, the higher the SPF rating, the more UV radiation is needed to produce a sunburn.
That’s mostly true, and indeed the low, every-day SPF 15 is where many recommendations start.
SPF numbers go all the way from zero to 100, but this is where things can become confusing for the average user. A “perfect score” SPF 100 product doesn’t do what many people expect.
For instance, many people think 100 means a 100 percent blocking of UV radiation, but that’s simply not true. SPF 100 provides around 99 percent coverage, while an SPF 50 still provides around 98 percent.
And believe it or not, SPF 15 can block more than 90 percent of radiation, according to some sources.
This is why many governmental organizations spend time trying to educate users on proper application.
Sunscreen is typically only good for a couple of hours of extended outdoor time, and a higher SPF isn’t going to negate improper application.
You don’t get 10 percent longer life out of an SPF 100 sunscreen than you do an SPF 90 sunscreen.
That said, SPF 15 is considered a broad spectrum sunscreen that, for most instances, is likely all you need on a normal day-to-day basis.
So, what should you use on your face? Well, it depends on what you’re doing. It depends on your skin type. It depends on your medical history.
Whether you’re fighting the signs of aging or a family history of skin cancer can make a huge difference in your SPF needs, and a healthcare professional is the best person to give you additional recommendations beyond what the CDC says.
That said, here are some guidelines:
An SPF 15 product will likely be adequate for most skin types in most casual situations. If you’re commuting, walking the dog, having brunch outside, driving a short distance with the top down or just making regular use of outdoor space — and you don’t have extenuating sensitive or dry skin needs — you should be fine with an SPF 15 and nothing more.
Longer durations in the sunlight should not necessarily be met with significantly higher SPF numbers, but rather with more religious and fastidious application.
If you’ve got an eight-hour day at the pool, you don’t need SPF 60 so much as you need to apply something every two hours, regardless of whether your daily sunscreen lotion is water resistant. And make sure to keep your skin dry when you apply it.
Now, that much time in direct sunlight and free of shade might also mean that a higher number is going to be your friend, in which case 30 or higher might be the right choice.
And the same goes for people who have more sensitive skin, or a family history that increases the risk of skin cancer.
The little things matter. That means that the proper application of normal or water-resistant sunscreen matters more than SPF.
It also means that reapplying SPF 30 after you get out of a pool is more beneficial than being lazy with a higher SPF.
It also means that you should check the expiration date, as many facial sunscreen options begin to deteriorate and lose protective ability after they’ve expired.
Will you get sick from using expired products? Probably not. Will you get burned? It’s much more likely.
Skin needs love, care, nutrition and protection, so a variety of treatments are needed to protect you from the sun and ward off premature aging of your skin.
Here are some things you can do alongside your daily SPF to preserve your youthful appearance:
Drink water. Studies show good water intake positively impacts your skin cells’ efficiency and health.
Clean your skin. Duh. To help diminish the impact of environmental pollutants, your skincare routine should include a cleanser to remove them before they cause damage. Also, a simple facial cream can even act as a barrier throughout the day, to add some protection from pollutants.
Quit smoking. Smoking is terrible for your skin. Read more information about resources for quitting, if you’re ready to quit.
Get more vitamin C. Your body needs vitamin C a few times a week to act as natural antioxidant protection and protect your cells. Our daily Morning Glow Vitamin C Serum brightens dull skin and adds additional vitamin C to your routine.
The short answer is: yes. It’s important to wear SPF whenever you’re going to be outside.
Believe it or not, it’s important even on cloudy days — if UV damage is gracing your skin with their presence, you should have some sort of protection on.
Your face needs a bit of support on the days where you’re going out for a quick walk around town, and SPF 15 is great for that.
But what’s more important is proper application. Yes, you may need a boost for that longer afternoon run, so a second layer might be advisable.
UV protection is about finding the right tool for the job, and with facial sunscreen products, that means active ingredients that can protect your face from developing age spots.
But it might also mean using some other tools to protect your facial skin.
Whether you dive into the world of daily SPF for your face or not, there are plenty of things you can do to protect your skin. Learn more about them from our How to Take Care of Your Skin guide.