Here’s What The SPF Rating On Your Sunscreen Actually Means

Here’s What The SPF Rating On Your Sunscreen Actually Means

But before we get to the numbers, a refresher on the SPF acronym itself: Sun Protection Factor.

So you think the higher the number the better it is at protecting your skin, but why? And before your mate’s sister’s best friend tries to tell you otherwise, no it is not the number of minutes it will take for your skin to burn.   

The SPF rating indicates the amount of potential UV radiation that is reaching the skin when sunscreen is applied according to directions. For example, SPF30 is estimated to filter 96.7% of UV radiation (meaning only 1/30th is reaching the skin). Whereas SPF50 is estimated to filter 98% of UV radiation (so only 1/50th is reaching the skin)*

Tiny difference in percentages, huge difference in fractions. And over a lifetime this really adds up. 

Under controlled conditions, like a laboratory, a sunscreen with higher SPF and broad spectrum coverage (filters both UVA and UVB rays) offers more protection against sunburn. But life ain’t like a lab. Instead a lot of sunscreen user-ers are lulled into a false sense of security when lathering on SPF50. So much so they tend to stay out in the sun longer, not apply as much in the first instance, and sometimes skimp on reapplication too. 

“When sunscreens are tested for SPF [under lab conditions], the product is applied at 2mg per cm2. This is roughly equivalent to seven teaspoons - 1 for each limb, chest, back and face for the average adult. Most of us do not apply sunscreen to the desired amount which effectively reduces the SPF. In actual fact, most of us are walking around with an SPF of a ½ to  ¼ of what is stated on the product. This also explains why aerosols and spray sunscreens are problematic, as it’s difficult to achieve the desired thickness of application with these formulations.” Explains Dr Annika Smith, Consultant Dermatologist at The Skin Hospital Darlinghurst. 

Rain, hail or shine you should be: applying sunscreen liberally to all exposed areas at least 20 minutes before going outdoors, reapplying every two hours, especially after swimming, sweating, or excessive towelling, seeking shade, wearing protective clothing and eyewear, and ordering too many potato scallops at lunch. (We added that last point, obviously.)

And while we’re expanding your knowledge on SPF might we just throw in this fact found on the Cancer Council page: the plus (+) in SPF50+ means more than. Sunscreen of this rating must provide at least SPF60 in testing because the same formula will always test slightly differently, in different labs with different methodology. So by aiming for SPF60 it removes any margin of error and ensures you are protected beyond what the bottle says. 

Some level of UV is always going to get to the skin. No sunscreen (yet) can completely block sunburn or the associated skin damage of being frequently outdoors. It is just one crucial part of protecting your skin. So wear it! The right amount! Every day!