How Much Water Is a Mole of Water?

How Much Does 1 Mole of Water Weigh?

Water drop
A mole of water is about 18 grams or 18 milliliters of water. Yamada Taro / Getty Images

How much is a mole of water? A mole is a unit of measuring the quantity of anything. It is simple to calculate the weight and volume of a mole of water.

Quick Mole Review

A mole is a unit of measuring the quantity of anything. A single mole is set to the number of particles found in 12.000 grams of carbon-12. This number is 6.022 x 1023 carbon atoms. The number 6.022 x 1023 is known as Avogadro's Number.


A mole of carbon-12 atoms has 6.022 x 1023 carbon-12 atoms. A mole of apples has 6.022 x 1023 apples.

A mole of water has 6.022 x 1023 water molecules.

Mass of 1 Mole of Water

How much water is that to most people?

Water (H2O) is made from 2 atoms of hydrogen and 1 atom of oxygen. A mole of water molecules would be 2 moles of hydrogen atoms plus 1 mole of oxygen atoms.

From the periodic table we see the atomic weight of hydrogen is 1.0079 and the atomic weight of oxygen is 15.9994.

Atomic mass is the number of grams per mole of the element. This means 1 mole of hydrogen weighs 1.0079 grams and 1 mole of oxygen weighs 15.9994 grams.

Water would weigh

weight of water = 2(1.0079) g + 15.9994 g
weight of water = 2.0158 g + 15.9994 g
weight of water = 18.0152 g.

One mole of water weighs 18.0152 grams.

Unless you have a good sense of mass, this value probably doesn't have much meaning to you. It's easier to grasp how much water is in a mole if you find the volume of this amount of mass.

Fortunately, this is another simple calculation.

Volume of 1 Mole of Water

To find out the volume of water in one mole, you need to know the density of water.

The density of water varies depending on temperature and pressure but can usually be taken as 1 gram per milliliter.

Density is the amount of mass per unit volume or:

Density = Mass/Volume

This equation can be rewritten to solve for volume:

Volume = Mass/Density

Plugging in the mass of 1 mole of water and its density gives you:


Volume = 18 grams / 1 gram/mL
Volume = 18 mL

18 mL holds a mole of water.

How much is 18 mL? It's not a lot! 18 mL is around the volume of a few drops of water. To put this in perspective, it's common to buy beverages in 1 liter volumes. 1 liter is 1000 milliliters.