Water weight calculator

What is water weight?

Water weight is simply how much a given amount of water weighs. Because fresh water has a density very close to 1 kilogram per liter at everyday temperatures, you can estimate the weight of water directly from its volume without any complicated measurement. This calculator takes a volume in liters and returns the weight in both kilograms and pounds, which is handy for aquariums, water tanks, cooking, shipping, and any situation where you need to know how heavy your water will be before you move or store it.

Formula

The estimate relies on the approximation that one liter of water weighs one kilogram:

Here $V$ is the volume in liters, $W_{kg}$ is the weight in kilograms, and $W_{lb}$ is the same weight expressed in pounds (since one kilogram equals about 2.20462 pounds).

How to use

1. Enter the volume of water in liters.
2. Read the weight in kilograms in the first result field.
3. Read the equivalent weight in pounds in the second result field.

The results update instantly as you type, and both fields stay empty until you enter a volume.

Worked example

Suppose you have 5 liters of water:

So 5 liters of water weighs about 5 kilograms, or roughly 11.02 pounds.

FAQ

Is 1 liter of water always exactly 1 kilogram? Not exactly. Water reaches its maximum density near 4 degrees Celsius, where 1 liter weighs almost precisely 1 kilogram. At warmer temperatures the same liter weighs slightly less, but the difference is small enough that the 1 liter = 1 kilogram rule works well for most practical purposes.

Does this work for salt water or other liquids? No. The 1 kilogram per liter approximation is specific to fresh water. Salt water is denser (around 1.025 kilograms per liter), and other liquids such as oil or milk have their own densities, so the weight would differ.

For related conversions, see our liters to quarts calculator and gallons to milliliters calculator.