The SPF number indicates how long you can stay in the sun without burning by simply multiplying your natural protection time.

Multiply by the SPF number to estimate how long you can be in the sun without burning.

First, start with a good sun block that has an SPF number of 30 or greater.

The higher the SPF number, the longer it protects a person from burning rays.

But beyond the SPF number, they don't know anything about sunscreen or what UVA light does.

The higher SPF numbers indicate greater protection.

SPF numbers start at 2 and have just recently reached 70.

While it is true that you don't double your protection when you double the SPF number, you do get an added benefit.

SPF numbers are determined through testing under very controlled environments using an amount of product that no one uses in the real world.

As a general rule, the higher the SPF number, the more protection against sunburn and other skin damage the sunscreen provides.