I'm not sure if this is the right forum category to post this, but I'm pretty sure this still has something to do with geometry. So I apologize in advance. Looking at soda/juice bottles, water containers, and even drinking cans has always make me wonder how do they (the manufacturing/bottling companies) exactly calculate the exact volume of their containers - which are considerably irregular in shapes that even have curves. The Coca-Cola bottle itself is known for its "sexy" form because of its curvature in the middle (more or less). So how can they say it's exactly "250 ml" in their bottles/containers, for example? What kind of math and engineering techniques do they use, to calculate and make these bottles? Thank you.