It’s one of the most persistent myths around sunscreens; that SPF 50 is only marginal better than SPF 30 and it’s therefore a ‘waste of money’ to pick SPF 50 This is NOT true. SPF 50 almost doubles the protection of SPF 30 And this is why: It’s often said that SPF 30 blocks 97% and SPF 50 98% of the UV light, BUT, when looking at SPF we are concerned with how much UV is still able to reach our skin to cause damage (swipe right). So we need to look at the transmission data which shows that doubling SPF from 30 to 60 halves the transmission from 3.3% to 1.7%, thus doubling protection. So half as much will reach the skin through an SPF 60. If we now have a look at the dynamic view (which takes into account the factor time) of how sunscreens work (swipe right), you can see that after 12 MED (2 h in Australian Sun), 80% of the sunburn dose is reached on the skin with an SPF 15, but only 40% when an SPF 30 is used. So the protection is doubled. This works the same as for SPF 30 versus 50. SPF 50 or SPF 30, which one should you chose? The higher the SPF in a sunscreen, a better chance you have of being properly protected. SPF 50 almost doubles the protection compared to SPF 30. But the big problem regarding the protection by sunscreens is that we don’t apply enough sunscreen and not frequently enough, meaning that the indicated SPF cannot be reached. It’s important to reapply your sunscreen every two hours regardless the SPF value. If you don’t like the texture of an SPF 50 or find it too expensive so that you don’t use enough of it, than it’s better to go for an SPF 30. But, if you would apply as much and as often of an SPF 50 than I would personally always go for an SPF 50. Which SPF do you use?