1 cubic kilometer of water contains 1 trillion liters of water. Therefore there are approximately 1,300,000,000,000,000,000,000 liters of water in the oceans, which is 1.3 sextillion liters. <br /><br /> To get to gallons, there are 3.78541178 liters in 1 gallon. Doing the math, that means there are 343,423,668,428,484,681,262 gallons of water in the oceans.