SPF 50 is adequate. Anything higher only marginally improves the protection.

For example:

• SPF 15 blocks 93% of UVB rays
• SPF 30 blocks 97% of UVB rays
• SPF 50 blocks 98% of UVB rays

Also there is a difference between UVB and UVA

It's not just the SPF that is important. It's also important how you apply and use the suncream is very important.

• Apply 30 minutes before going outside
• Reapply often, every two hours
• Make sure you put enough on.