SPF Factor Explained - What is it and How Does it Work?

Summer is here and we are all soaking it all in and enjoying those warm rays of sunshine while they last.  We all know to grab our sunscreen before diving into the dazzling light…but why exactly? And when? And how much? And which one? And what do those pesky SPF numbers even mean? 

It can seem so complicated, but we’re here to clear it all up!

What is SPF?

We love the sun, but it's UV, or ultraviolet rays (UVA + UVB)  can cause some serious damage to our skin.  UVB rays are the sun rays most commonly responsible for sunburns and skin cancer.

SPF is the acronym which tells us how much protection we are getting from the sun. It stands for “Sun Protection Factor”, and is a measurement of protection from UVB exposure. 

Here is How They Compare:

So...What Does This Mean?

Though good to know, these numbers for most of us only make us a little   more confused.  Though not technically a determination of time, it is easier to look at SPF as basically a measurement of how much longer you can stay in the sun without damage. 

For example, If you can normally be outside for 10 minutes before burning, an SPF of 15 will allow you 150 minutes, an SPF of 30 for 300 minutes etc. An SPF of 100 would technically protect you for 1000 minutes, or almost 17 hours…that’s more hours than we have sunlight!

Sounds great, right? 17 hours! That must be the one to choose, right? No.  Why? Because even though those numbers seem great, the practical matter is that your sunscreen will wear off long before those hours are up, and the false sense of extended protection can lead to staying out in the sun longer, skipping re-applying and not covering up creating even more UV damage, which defeats the purpose.  An SPF of 30 is what most health experts recommend.

The Problem with a Higher SPF

According to the EWG (Environmental Working Group) sunscreens with SPF values of 50+ are more problematic as consumers trust these high SPF products too much.  Many studies have found that people are more likely to use high SPF products improperly and, as a result, may expose themselves to more harmful ultraviolet radiation than do people who rely on products with lower SPF values.  Hence, an SPF of 30 is recommended.

Instead of a one and done approach with sunscreen, it is better to choose a lower SPF and apply often, at least every 2 hours and after any activity that gets you wet or makes you sweat!

For more information on how to properly apply sunscreen read our 2022 guide on How to Apply Sunscreen and other safety tips!