Many of us have probably experienced squeezing out what we think might be way too much sunscreen, and so we desperately try to smear the extra on the closest person, or shove some back into the bottle (with no luck).
As it turns out, we may actually need all of that...and more.
According to this article by the Skin Cancer Foundation, the general recommendation is 2 milligrams of sunscreen per square centimeter of skin. In plainer terms, that's about 30g of sunscreen, or enough to fill one shot glass (or two tablespoons). What's more, you should save one small dollop for the face alone.
If you use a non-cream type sunscreen, such as a spray, apply enough until an even sheen appears on the skin. The trouble with sprays is, you can't really know whether you've used enough of it.
How much sunscreen should I be using on my face and body? [Skin Cancer Foundation]