How High of an SPF Does Your Sunscreen Need To Have?

how high of an spf does your sunscreen need

How high of an SPF does your sunscreen need to give you good protection from UV rays? You know that wearing sunscreen daily is one of the most important anti-aging and preventative health moves you can do for your skin. It’s important to pick the best product and people ask for my advice to help them do that. One of the biggest sunscreen questions people have is about SPF numbers.

Common sense, AND what you learned about numbers in math class, would lead you to believe that sunscreens with really high numbers must give really powerful sun protection, right? 

Sunscreen companies would like you to believe that too, but.......

Why doesn’t a SPF 60 sunscreen give you twice as much sun protection as a SPF 30?

Pure mineral zinc oxide water resistant SPF 50 sunscreen

Answer: The protection you get isn't proportional to the numbers.

Get dermatologist-approved sun protection from my Water Resistant Sheer Strength Pure Physical Spray SPF 50 Sunscreen

Does the SPF 30 vs. 50 matter? Is it enough? What sunscreen do I - a dermatologist - use for my skin?

Find out what you should look for and stop being fooled by misleading product marketing claims. Pick the best sunscreen for your skin, wear it daily, know you’re protected, and your skin really will look fabulous as you age. - Dermatologist Dr. Bailey


Important facts for understanding your sunscreen needs:

  • UVB is the sunburn ray. You’re most exposed when you're close to the sun because UVB rays are absorbed as they pass through the earth’s atmosphere-the closer you are to the sun the stronger the UVB.  It’s why the sun is more intense near the equator, at high altitude, in summer and at mid-day.
  • The SPF value indicates how well your product protects you from UVB.

Dermatologist explanation of how sunscreens work.

How do chemical sunscreens block UV rays?

  • Organic sunscreens absorb into your outer dead skin cell layer and use a chemical reaction to block UV rays from passing farther into your skin. (The term 'organic' doesn’t mean natural, it means not mineral.)
  • You feel this reaction as warmth, which is why organic sunscreens may make you feel a little extra hot in the sun. 
  • The organic chemicals break down during this sun blocking chemical reaction, which is one reason why sunscreen products tell you to reapply every 2 hours when you're out in the sun.
  • All the 'active ingredients' listed on sunscreens that are not zinc oxide and titanium dioxide are chemical sunscreen filters. 

How do mineral (physical) sunscreens block UV rays?

  • Mineral sunscreens sit on top of your skin and bounce the sun off, without a chemical reaction and without creating the warmth. 
  • Mineral sunscreens include zinc oxide and titanium dioxide.  Years ago, mineral sunscreens were white on the skin.  Today's modern versions are made with high-tech formulations so that the mineral particles don't clump together. Instead, they distribute evenly and invisibly over your skin surface.
  • Mineral UV filters don't pass into your skin
  • Zinc oxide and titanium dioxide to not readily break down when they block the sun so their sun protection last longer on your skin.

Both organic and mineral sunscreens can block UVB well and can provide the same SPF values. 

The amount of UVB protection isn't proportional to the SPF number.

Is SPF 4 sunscreen really different from SPF 15 or 30?

Said another way, what is the percentage of UVB that’s blocked from your skin compared with your product's SPF value?

 SPF 2 50% of UVB rays are blocked
SPF 4 75% of UVB rays are blocked
SPF 10 90% of UVB rays are blocked
SPF 15 93% of UVB rays are blocked
SPF 30 97% of UVB rays are blocked
SPF 50 98% of UVB rays are blocked
SPF 70 98.5% of UVB rays are blocked
SPF 100 99% of UVB rays are blocked

Notice that once you hit an SPF of 10 a sunscreen blocks 90% the percent of UVB rays. After that, the percent of UVB blocked doesn’t go up very much as the SPF numbers go up.  The sweet spot is SPF 30 where 97% of the UVB rays are blocked, and most dermatologists agree.

Remember, to get the actual SPF protection from sunscreen you must apply the correct amount of sunscreen.

This is a really important point to understand. For the average adult, that means 1 oz (a shot glass) per application when in a bathing suit, and reapplied every 2 hours or after water contact.  That means a day in the beach should use up ½ to ¼ of an 8 oz. bottle of sunscreen! My sunscreens give you an SPF 50 to give you a little added protection in situations where you are not putting enough on or not reapplying it as often as we recommend. 

Plus, organic sunscreens break down as they block the UV rays. Mineral sunscreens are structurally more durable and can last longer on your skin.  They are usually combined in products with organic sunscreen ingredients so we still recommend reapplication every 2 hours, but I think the added protection matters. All the dramatic sunburns that my patients have brought to my office over the years happened with the use of 'organic' sunscreens. 

UVA protection is critically important for anti-aging and skin cancer prevention. 

UVA skin damage:

  1.  UVA causes the wrinkles and skin thinning that most people think come with age
  2.  UVA plays a role in causing skin cancers

To know if a sunscreen blocks UVA look for the word 'Broad Spectrum' on the front label.

how high an spf does your sunscreen need explained by dermatologist dr cynthia baileyUVA is very damaging to skin. The UVA rays are out all day, all year, and the SPF on a product tells you very little about UVA protection.  A sunscreen product can claim to give UVA protection even if it doesn’t protect you from all the bad UVA rays.  Look for a product labeled Broad Spectrum AND SPF 30 or higher to be certain you are also getting good UVA protection. I also recommend that the product be formulated with at least 5% or more zinc oxide because:

  • Zinc oxide is the only ingredient that blocks all the way through the UVA wave spectrum to 400nm, though titanium dioxide goes almost to 400nm too.
  • So far, the organic UVA sunscreen ingredients like avobenzone have stability trouble and may not last in the bottle and on your skin, and we don’t yet have ways to measure this.

What is my opinion on sunscreens, and the ‘bottom line’ as a careful dermatologist?

An SPF 30 that includes 5% or more of zinc oxide, applied every day, will take good care of your skin.

Links to sun protection products that I, as a dermatologist, use and recommend to my dermatology patients:

See all the Sunscreens that I use in my practice.

Some of my favorite sun protection products and kits include:

My Sheer Strength Pure Physical Sunscreens: these sunscreens offer the best sunscreen advances available today.

Dermatologist recommended best facial SPF 50 sunscreen contains iron oxide! 

best tinted facial sunscreen spf

I have a Matte Tinted SPF 50 sunscreen for daily wear. The tinting comes from over 3.2% iron oxide which also helps block visible and digital screen light known to damage skin over time. This non-greasy sunscreen feels weightless on your skin. It blends into all skin tones and provides water resistant protection - aka hot, wet and sweaty activity protection!  And, it looks great on your skin. 

The easiest way to reapply facial sunscreen during the average day

best powder mineral sunscreen spf 50

Reapplying facial sunscreen is tricky, especially if you wear makeup. The best way to do it is by using a powder sunscreen. I have a Powder Refresh SPF 50 Sunscreen for easy reapplication on days when you are out for extended time but can't reapply a cream or liquid sunscreen.

Water resistant spray sunscreen for the entire family

When you are doing wet and sweaty activities, you need a water resistant sunscreen. I have the perfect fragrance-free highly water resistant pure mineral spray spf 50 sunscreen when it's time for serious fun in the sun for the entire family. It's easy to apply - and reapply - because it comes in a spray bottle. Always smear and rub spray sunscreen into skin for even application!

best water resistant reef safe spf 50 sunscreen

My Sheer Strength Sunscreens are not regular sunscreens like ones you've used in the past. Nope! The advanced mineral technology makes these easy to wear, non-irritating and they provide superior protection compared with sunscreens you've used before. - Dr. Bailey



how high SPF do you need for sunscreen



Don't forget to wear a hat!

Get everything you need in my SunSavvy Around Town Kit: Great daily wear sun protection products including 2 sunscreens that are pure mineral products: my matte tinted facial sunscreen, my water-resistant spray sunscreen. I include a great sun hat and my Detecto Ring to test UV ray exposure. 


To see all of my dermatologist-recommended sun protection products click here. These are the products I trust for my patients, my family and my own skin.

Photo: NASA Goddard Photo and Video