LOS ANGELAS, CA (Consumer Reports) – If you buy your sunscreen based on its SPF rating, you may be getting shortchanged. New testing from Consumer Reports reveals not every sunscreen meets their SPF claims.

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

“Whole body. Everything [and] anything that the sun is touching. I wear sunscreen on my face every day; even my make-up has sunscreen in it,” claims Paraita.

Many people choose their sunscreen based on the SPF factor.

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

But according to new testing by Consumer Reports, you may not be getting the bottle’s promised protection.

“About 1/3 of the sunscreens we tested this year did not meet their SPF claims,” reports Trisha Colvo with Consumer Reports.

SPF measures how well a sunscreen protects your skin from the sun’s harmful ultraviolet rays. Of the 34 sunscreens tested by Consumer Reports, 11 did not meet their SPF claims. Calvo says that could lead to a false sense of security for consumers.

“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,” says Calvo.

Experts say that’s why it’s important to reapply sunscreen, and the best way to protect your skin is to limit your time in the sun.

Consumer Reports says they don’t recommend shopping by brand, because their tests found some sunscreens from particular brands did well while others from the same brand did not.