What SPF should I use?
May 23, 2025
Medically Reviewed | Last reviewed by Saira George, M.D., on May 23, 2025
Sunscreen helps protect your skin from ultraviolet (UV) radiation. But which SPF is best?
MD Anderson dermatologists recommend sunscreen that is at least SPF 30, broad-spectrum and water resistant. Even with those guidelines, there are plenty of options to choose from. They may even prompt questions like, “If SPF 30 is good, does that mean SPF 50 or even SPF 100 is better?”
I always like to remind patients that sunscreen – no matter what SPF you choose – is only one part of sun protection. Ahead, we’ll talk about SPF and how to use it as part of a larger sun safety routine.
How is SPF determined?
SPF levels are determined by laboratory testing. Sunscreen is applied to a designated patch of skin before it’s exposed to an ultraviolet light source that simulates sun exposure. Then, the time it takes the sunscreen-protected skin to redden or burn is carefully measured and compared with the time it takes a similar area of unprotected skin to redden or burn. The testing protocol specifies everything from the amount of sunscreen applied per area of skin to the type of light source that is used. This is done to standardize measurements and make it easier for shoppers to compare sunscreens using their SPF levels.
In laboratory SPF testing, small areas of skin are covered in a uniform, thick layer of sunscreen. But real-life conditions — like a day at the beach or an afternoon spent by the pool — are not controlled like they are in the laboratory. People tend to underapply sunscreen, apply it unevenly and forget to reapply it before it wears off or gets rubbed off. Likewise, conditions like the intensity of UV exposure can change. This means most of us won’t reach the sunscreen’s level of SPF in everyday use.
How much protection does SPF provide?
Sunscreens help protect our skin by reflecting or absorbing the ultraviolet rays that cause sunburn and skin damage. SPF numbers give us an idea of how much protection a sunscreen provides and how it compares to other sunscreens. A higher SPF means a sunscreen can absorb or reflect more sunburn-causing UVB rays to prevent you from getting burned than a lower SPF sunscreen can.
Double the SPF number doesn’t mean double the protection, however. This is because the amount of UVB blocked by sunscreen is not linear. In other words, after a certain point, a higher SPF number may only provide a little more UVB protection.
For example,
- SPF 15 blocks 93% of UVB rays
- SPF 30 blocks 97% of UVB rays
- SPF 50 blocks 98% of UVB rays
Likewise, after a certain point, less extra UV exposure is needed to cause more damage to your skin.
Think of it like layering clothes in a blizzard. The first few layers make a huge difference in blocking the cold. After that, the third and fourth layers provide additional protection, but proportionally less than the first layers did.
What do these sunscreen terms mean?
Sometimes it can seem like you need a dictionary to read sunscreen packaging. Here’s what some common sunscreen terms mean.
Broad-spectrum
MD Anderson dermatologists recommend choosing a broad-spectrum sunscreen. This means that the sunscreen protects from two different types of sun rays that can damage skin: UVA and UVB.
UVA exposure leads to skin tanning, pigmentation and oxidative damage that can contribute to photoaging and add to the cancer-causing effects of UVB.
UVB exposure is the main cause of sunburn and can lead to skin cancers, including melanoma, basal cell carcinoma and squamous cell carcinoma of the skin.
Water-resistant
If you are swimming, sweating or splashing, MD Anderson dermatologists recommend choosing a water-resistant sunscreen. The Food and Drug Administration (FDA) regulates sunscreen products and writes that water-resistant products are labeled as providing their SPF levels for either 40 or 80 minutes, even in wet conditions.
Don't forget: You still need to reapply water-resistant sunscreen just as frequently as sunscreen that isn’t water-resistant.
PA++++
Sunscreens labeled as ‘broad-spectrum’ have been tested to protect against UVA and UVB rays. The PA++++ index is a newer, separate rating that means additional testing was done to quantify how much UVA protection a sunscreen provides. It is based on a number called the UVA-Protection Factor (UVA-PF), which is like SPF but for UVA rays. The ranking goes from less protective to more protective: PA+ to PA++++. So, choose PA++++ for the most UVA protection.
Key takeaways:
- Choose a sunscreen that is at least SPF 30, broad-spectrum and water resistant.
- A higher SPF number provides only slightly higher benefits.
- Reapply sunscreen every two hours – sooner when swimming or sweating.
Does skin tone matter when selecting an SPF level?
Having darker skin means you start with a base layer of protection that someone with fair skin or who burns easily doesn't have. But people with darker skin can still get sunburn and are still at risk for skin cancer or sun damage.
RELATED: Can dark-skinned people get a sunburn?
So, while using a higher SPF may be relatively more beneficial for someone with fairer skin than for someone with darker skin, don’t skip sunscreen altogether. In general, broad-spectrum SPF 30 products provide a good level of UV protection for everyone.
Does sunscreen type matter?
It’s wonderful that we have so many sunscreen options because it makes it easier to find one you don’t mind wearing.
Choose a sunscreen you can apply correctly to all your exposed skin to get the most out of the sun protection level indicated by its SPF. I typically recommend lotion and cream sunscreens. This is because it can be harder to get effective coverage with spray or powder products. They can also be accidentally inhaled or get into sensitive areas like the eyes.
Does SPF level determine how often I need to reapply my sunscreen?
No. Regardless of what SPF level you choose, you should reapply every two hours or after sweating or swimming. Check the Drug Facts label on your sunscreen for specific instructions.
My makeup has SPF. Do I need to apply more?
While the SPF in makeup and skincare products helps protect your skin from sun damage, it doesn’t always offer the full SPF 30 recommended by MD Anderson dermatologists.
Cosmetic products with SPF 15, like primers or foundations, are a nice base layer of protection from everyday sun exposure to your face like the kind you might get walking your dog in the morning. However, most people will need additional dedicated sunscreen for activities like a day at the beach or an outdoor baseball game.
Don’t forget to apply sunscreen to exposed skin that your makeup doesn’t cover. And remember to pack extra sunscreen to boost the coverage of your makeup products. Reapply every two hours or after being in the water or breaking a sweat.
Do I need to do anything besides wearing sunscreen?
Heading outdoors for a long time or during peak UV hours? Try to minimize how long you are in direct sun between the hours of 10 a.m. to 4 p.m. by seeking shade or coming indoors if you can. In addition to wearing sunscreen, I recommend wearing:
- A hat
- Sunglasses
- Sun-protective clothing, such as UFP items, or articles that are dark-colored and made of dense material.
Shop for MD Anderson branded UPF gear.
Remember, sunscreen is just one way you can protect your skin from the sun, not the only way.
Request an appointment at MD Anderson online or call +1 346 503-2729.
In general, broad-spectrum SPF 30 products provide a good level of UV protection for everyone.
Saira George, M.D.
Physician