Water is an essential element of life. We all living things can't survive without water and food. We can live without food for a week but without water, we can't live for more than 2 days because water is essential for our body. Here we are talking about the measurement of water in a gallon. There are different sizes of gallons for different locations like the US has own gallon size while UK may be different from the US.So Here we will talk about How much a does US Gallon of water weigh? in pounds or kgs. The research we conduct from different sites of science and measurement we have got that the normal Us gallon has 8.34 lbs or 3.78 kg weight at 17 °C. Note that water has the temperature effect also. As the weight of water in cold will be different where the water could freeze or in summer it could be different because of water density.