The American Academy of Dermatology recommends 1 ounce (1 shot glass or two tablespoons) of sunscreen for your entire body. The Skin Cancer Foundation, suggests approximately two milligrams of sunscreen per centimeter of skin. For the face, approximately a quarter size dollop should be sufficient for the entire face, neck, and décolleté. If you have further questions about sun safety, consult with your physician or qualified healthcare provider.