By Stephanie Stahl

By Stephanie Stahl

PHILADELPHIA (CBS) — Sunscreen is the best way to stay safe in the sun.

But new testing reveals the SPF number on the label isn’t always accurate, some missing the mark by 70 percent.

You might be unknowingly be putting yourself at risk.

Bailey Peraita depends on sunscreen to keep her skin protected from the sun.

“Whole body, everything anything that the sun is touching, I wear sunscreen on my face every day even my make-up has sunscreen in it,” said Peraita.

Many people choose their sunscreen — based on the SPF number, that’s the sun protection factor, a measurement of how long the product will guard against UVB rays.

“I like to aim for 15-30, but I prefer a higher number,” said Christina Given.

An SPF of 30 or higher, blocks 97 percent of the suns damaging rays, the primary cause of skin cancer.

But according to new testing by Consumer Reports, you may not be getting the promised protection, with the SPF on the label.

“About 1/3 of the sunscreens we tested this year did not meet their SPF claims,” said Trisha Calvo, Deputy Editor for Health & Food at Consumer Reports.

Of the 34 sunscreens tested by Consumer Reports – 11 did not meet their SPF claims.

That’s potentially dangerous, giving people a false sense of security.

“When you have something that’s an SPF 30, and it tests at below an SPF 15, that’s worrisome because you’re getting less protection than what most dermatologists and experts recommend,” said Calvo.

One baby formula that was tested said it had an SPF of 100, but it was only 18.

While a third of the sunscreens tested didn’t measure up, 70 percent did provide the SPF protection that was on the label.

Consumer Reports findings:

La Roche-Posay’s Melt-In Sunscreen Milk got a perfect score of 100 but cost the most of those tested, at $36 for a five ounce bottle.

The good news is that some of the most effective products are also the lowest priced.

The other sunscreens that passed the test were:

– Copper Tone Water Babies SPF 50 ($10.50)

-Equate (Walmart) Ultra Protection SPF 50 ($9)

– Vichy Capital Soleil Light Weight Foaming Lotion

-Banana Boat SunComfort Continuous Spray SPF 50+ ($11)

Consumer Reports says eleven of the sunscreens didn’t meet their SPF claims, and eight of them had an SPF below 30. Brands like BabyGanics, Eltamd, Hawaiian Tropic, and Walgreens failed to meet what they claimed, and had SPFs of lower than 30. Some of the other sunscreens that didn’t make the cut were:

-VaniCream SPF 50+

-Banana Boat Sport Performance Power Spray SPF 100

-CVS Baby Pure & Gentle SPF 60+

Stephanie Stahl