Main assumption: We’re talking about water/air above the earth’s surface. The volume of oceans, seas and bays (constituting about 97.3% of all water) on earth is roughly 1.3 billion cubic kilometers, or 1.3E+15 cubic meters (cu.m.). read more
Square kilometers of water was easy, as a google search quickly revealed all of our ocean is 355 million square kilometers of water. The freshwater, its 3.5% of all ocean water. So, 350,000,000+ (350,000,000*3.5), equates to about 1,575,000,000. read more
The oceans contain 96.5% of all water. The total volume of water on Earth is estimated at 1.386 billion km³ (333 million cubic miles). This represents 0.22 % of the total mass of the Earth. More: About 97.5% of water on Earth is salt water and 2.5% fresh water. Of the 2.5% fresh water, only 0.3% is in liquid form on the surface. read more