Is SPF 30 enough, or do I need SPF 50?

SPF 30 blocks roughly 97% of UVB and SPF 50 blocks about 98%, the real-world difference is small assuming you apply enough product. Across reviewers, the more meaningful issue is under-application: most people use far less than the tested 2 mg/cm². Choosing a higher SPF (50+) gives a buffer for that.