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

On this page:

• How much does water weigh?
• How much does 500ml of water weigh?
• Calculating the weight of water
• Water density chart

How much does water weigh?

The weight of a volume of water depends upon the temperature at which it is being stored. This is because water expands as it gets warmer, meaning that hot water weighs less, and cold water weighs more (because it's more dense).

Water reaches its highest density at a temperature near freezing. As it begins to freeze, it starts to expand and therefore becomes less dense again.

In order to accurately convert a volume of water to a weight in grams, ounces or pounds, a density figure needs to be factored in. ¹

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

To calculate the weight of a gallon of another liquid, you can use our gallons to pounds converter.

How much does 500ml of water weigh?

500ml of water at room temperature (70°F / 21°C) weighs approximately 500 grams (17.6 ounces or 1.1lb). This is because the density of water at room temperature is around 1g/ml (0.99802 g/ml).

How much does a 16.9 oz bottle of water weigh?

A 16.9 fl oz bottle of water at room temperature (70°F / 21°C) weighs approximately 17.595 ounces, or 1.1lb, plus the weight of the bottle. For a plastic 16.9 oz bottle of around 0.35 ounces (0.022lb), you're looking at a total weight of around 17.95 ounces or 1.12lb.

These conversions reference the US fluid ounce (29.57ml) rather than the UK Imperial fluid ounce (28.41ml).

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, ensure that your volume figure is converted to milliliters (mL).

Example: 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 = 1000mL
2. Weight in grams = volume × density
   1000 × 0.99802 = 998.02g
3. Convert grams to pounds
   998.02 × 0.0022 = 2.1956 lb

To make things easier, and assuming you require 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. If you need help with your conversion, you can use our ml to grams conversion tool.

Water density chart

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. ²

Calculator created by Alastair Hazell

References

1. The Physics Factbook. Density of Water. Edited by Glenn Elert.
2. United States Geological Survey. Water Density. Water Science School.
3. PET Resin Association. Little-Known Facts about PET Plastic.