What Is SPF and What Does It Stand For?

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What Is SPF and What Does It Stand For?

You’re about to make your next sunscreen purchase and are scanning through a selection of bottles ranging from SPF 30 to SPF 70. What exactly is SPF and how should it inform your decision-making? This guide should provide all you need to know about the SPF rating system, better known as “Sun Protection Factor.”

What Does the SPF Number Mean? 

A common misperception is that the SPF number on a bottle signifies the amount of time you can spend in the sun without getting burned (30 minutes for SPF 30, 50 minutes for SPF 50 etc.) This is not accurate. In fact, the SPF rating system is far more complex and based on the degree to which a certain formula protects against the sun’s harmful UVB rays over a certain period of time. For example, a sunscreen with a rating of SPF 30 allows only 3 photons per 100 to penetrate the skin, meaning it shields approximately 97% of the sun’s harmful UVB rays over a two-hour period. This roughly translates to 30 times the protection you’d have versus using no sunscreen at all.  

This extends to SPF 50 (98% or 50 times the protection) and SPF 70 (98.5% or 70 times the protection). The general consensus is that SPF 30 is the minimum SPF rating for adequate sun care protection.

Does Higher SPF Matter? 

Most experts agree that SPF 30 — when applied properly — should provide adequate sun protection for most people. However, sunscreen misuse is common, so SPF 50 or 70 does help provide “extra insurance” for those times when you forget to follow the “How to Properly Apply Sunscreen” manual. This manual would tell you to use about a shot-glass (1.5 ounces) amount of sunscreen, rub in thoroughly to all exposed parts of the body and reapply every two hours or after swimming.  

How Does SPF Work? 

No sunscreen protects you from 100% of the sun’s harmful rays, but they do get close. The active ingredients in sunscreen (both mineral and non-mineral actives) protect us in two different ways: by either reflecting the sun’s harmful rays or by absorbing them. Mineral sunscreens reflect or block; non-mineral sunscreens absorb. Sun Protection Factor is calculated by measuring the factor in which a user is protected from the sun versus using no sunscreen at all. 

How to Choose the Right SPF 

The right SPF for you really comes down to the outdoor activity. If you’re simply going to be in the sun walking or laying out, an SPF 30 applied correctly every two hours should suffice. If you’re going to be involved in any activity in and around water or that makes you sweat, we recommend SPF 50 or higher with more frequent re-application.   

What SPF for Your Face? 

Your face is on the front lines of sun exposure and does benefit from a more meticulous application routine and a higher SPF. We recommend SPF 50 or higher on the face, both as part of your daily skin care routine and re-applied every time you head outside. 

SPF Sunscreen FAQs:

Is SPF 100 Really Better Than SPF 50? 

While SPF 100 will protect you more than SPF 50 sunscreen, “better” is a relative term here. SPF 50 protects you from 98% of the sun’s harmful rays. SPF 100 protects you from 99% — relatively negligible, but a worthy investment for those who want to maximize their sun-care efficacy at all costs.  

Will You Still Tan With SPF 50? 

Since no sunscreen provides 100% protection from 100% of the sun’s UV rays, wearing sunscreen does not mean you won’t tan. How fast and how dark you tan while wearing sunscreen will vary by individual. But even if you’re diligently wearing sunscreen, extended time in the sun will likely result in some tanning over the long term.

Is It OK to Apply SPF Every Day? 

In short: applying SPF to your everyday skin care routine is highly recommended. As we continue to learn more about UV rays’ harmful effects on the skin even after short amounts of time outside, daily SPF application is becoming more commonplace.