S.P.F. is the major factor used in determining U.V. protection levels. This means that a higher S.P.F. number is usually higher protection from the sun. S.P.F. levels range from two to 100, but the higher you go above 30, the smaller the difference becomes. For example, S.P.F. 30 offers 97% protection, S.P.F. 50 offers 98% protection and S.P.F. 100 offers 99% protection.