Question: how many molecules of water on earth?
Answer: That means, per droplet, you have to divide that number by 24,000 because there are 24,000 droplets in a litre. So there must be 1.39 X 1021 molecules of water in an individual droplet of water, which is an amazing number of molecules. The volume of the Earth's oceans is 1.37 X 109 cubic km.