SPF means Sun Protection Factor. This number is the ‘factor’ you multiply times the amount of minutes your skin usually takes to burn.

If your skin naturally burns in 5 minutes, and SPF of 30 means you have 30 times the number of minutes you burn naturally. So, in this case - you will be protected for about 150 minutes (2.5 hours).

If you naturally burn in about 10 minutes, that’s 300 minutes of protection (5 hours).

Minutes to burn without sunscreen x SPF number = maximum sun exposure time.