Everything you know about SPF is wrong.

What does SPF 30 really mean?

SPF stands for "Sun Protection Factor." It measures how effectively a sunscreen product can protect your skin from the harmful effects of ultraviolet (UV) radiation- sunburn, skin damage, increased risk of skin cancer, etc.

The SPF number you see on products ONLY measures protection against UVB rays (not UVA rays). The higher the SPF number, the greater the level of protection the sunscreen provides. The "F" (Factor) is a very important concept here. SPF 30 does NOT imply that your skin is protected for 30 mins. Instead, SPF 30 means that it admits 1/30th (or 0.033333333 or ~3%) of ambient UVB radiation. To put it another way, SPF 30 gives you 97% protection. 

SPF 30 means that it admits 1/30th (or 0.033333333 or ~3%) of ambient UVB radiation. To put it another way, SPF 30 gives you 97% protection. 

Let's continue fleshing this out:

• SPF 15 gives you about 93% protection

• SPF 30 gives you about 97% protection

• SPF 50 gives you about 98% protection

It's important to note that while higher SPF provides more protection, no sunscreen can offer 100% protection from UV radiation.

http://www.mpgillusion.com/2012/07/sunscreen-spf-and-diminishing-returns.html

Protection vs Price

As you can see, the SPF scale is not linear. That begs the question, is there a point of diminishing returns?

As SPF numbers start to sound very impressive (from 30, to 45, to 60, to 100) the actual increase in skin protection is negligible.

So, although an SPF of 60 may seem "twice as good" as an SPF of 30, it is adding only 1% more protection. You can, however, bet that the price is increasing more than 1%.

If you have to pay 30-50% more to get only 1% more protection, is it worth it? 

Products with very high SPFs also create a false sense of security. People who use them tend to stay out in the sun longer and skip reapplying. Some think they don’t need to seek shade, wear a hat, or cover up with clothing. They end up getting a lot more UV damage, which, naturally, defeats the purpose.

Hot Tip

Be a smart consumer. Buy SPF 30 sunscreen (97% protection), save money, and use the savings to reapply sunscreen often, as its effectiveness diminishes due to activities like sweating and swimming.

Unfortunately, there's no way around it. You should reapply sunscreen every two hours, no matter the SPF. So find a sunscreen you love- and stay sun smart!

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