I have read a lot about this believe it or not. lol. They always say when having sex, you burn less calories than when walking. There are a million factors when trying to figure out a number of calories burned (wieght, metabolism, body heat, heart rate, etc). When a tredmill or something is telling you how many calories you burned, its just an estimate used. The question is like asking how many grams will I get from an indoor plant.