Water Weight Calculator

Calculate the weight of a gallon, liter, cup or tablespoon of water in pounds, ounces, grams and kilos.

How much does water weigh?

The weight of water varies depending upon the temperature at which it is being stored. To give a simple explanation, hotter water weighs less, and colder water weighs more (because it's more dense). In order to accurately convert a volume of water to a weight, a density figure is therefore required.

At room temperature (70°F / 21°C), the density of water is 0.99802 g/ml. This means that for a US gallon of water at room temperature, the weight would be around 8.33 pounds. How much does a gallon of water weigh?

Calculating the weight of water

To work out the weight of a container of water, you'll need a couple of figures: the volume of water and the density of the water (ideally in g/ml, for this example). Before you begin your conversion, you'll need to ensure that your volume figure is converted to milliliters (mL). You can use the liquid volume converter if you need to make a conversion. Let's move on to our example of how to convert:

Example: For 1L of water at room temperature

Water density at room temperature: 0.99802 g/ml

1. Convert your 1L figure to mL
   Volume = 1 × 1000 = 1000 mL
2. Weight in grams = volume × density
   1000 × 0.99802 = 998.02g
3. Convert grams to pounds
   998.02 × 0.0022 = 2.1956

To make things easier, and assuming you're after a rough estimate, you could use a straight density figure of 1g/ml. This assumes a water temperature of 39.2°F / 4.0°C.

Water density

The following water density figures are from the U.S. Department of the Interior, Bureau of Reclaimation, 1977, Ground Water Manual, from The Water Encyclopedia, Third Edition, Hydrologic Data and Internet Resources. They are sourced from the United States Geological Survey.