Water Weight Calculator – How Much Does Water Weigh?
Find how much water weighs given a volume in teaspoons, tablespoons, cups, quarts, pints, gallons, liters, or milliliters.
On this page:
- Water Weight Calculator
- How Much Does Water Weigh?
- How to Calculate the Weight of Water
- Weight of Water for Different Volumes
- The Temperature Affects the Weight of Water
- Density of Water at Various Temperatures
- How Much Does a Gallon of Water Weigh?
- How Much Does 5 Gallons of Water Weigh?
- How Much Does One Molecule of H2O Weigh?
- H2O Molar Mass
How Much Does Water Weigh?
The weight of a volume of water can be found given the density, which is the mass compared to the volume. The density of water is 1 kilogram per liter (kg/L) at 39.2°.
This means that 1 liter (L) of water weighs 1 kilogram (kg) and 1 milliliter (mL) of water weighs 1 gram (g).
In common US measures, one gallon of water weighs 8.345 pounds.
The density of water varies slightly at different temperatures which will impact the weight of for the same volume.
How to Calculate the Weight of Water
To find the weight of water, start by finding the density(1 kg/L at 39.2°) and the volume of water. Convert the volume of water to liters and then multiply by the density to find the weight. Use our volume conversion calculators to convert different volumes to liters.
volume = 10 mL
volume = 10 mL ÷ 1000 = .01 L
density = 1 kg/L
weight = .01 kg
weight = .01 kg × 1000 = 10 g
1 gram is equal to 0.035274 ounces so to get a result in ounces simply multiply the grams by 0.035274. You can also use our weight conversion calculators to convert from grams and kilograms to pounds and ounces.
Weight of Water for Different Volumes
|Volume||Weight (oz)||Weight (lb)||Weight (g)||Weight (kg)|
|1 teaspoon||0.1739 oz||0.0109 lb||4.929 g||0.004929 kg|
|1 tablespoon||0.5216 oz||0.0326 lb||14.787 g||0.0148 kg|
|1 cup||8.345 oz||0.5216 lb||236.59 g||0.2366 kg|
|1 pint||16.691 oz||1.043 lb||473.18 g||0.4732 kg|
|1 quart||33.382 oz||2.086 lb||946.35 g||0.9464 kg|
|1 gallon||133.53 oz||8.345 lb||3,785.4 g||3.785 kg|
|1 milliliter||0.0353 oz||0.002205 lb||1 g||0.001 kg|
|1 liter||35.274 oz||2.205 lb||1,000 g||1 kg|
|1 cubic inch||0.578 oz||0.0361 lb||16.387 g||0.0164 kg|
|1 cubic foot||998.85 oz||62.428 lb||28,317 g||28.317 kg|
|1 cubic yard||26,969 oz||1,685.6 lb||764,555 g||764.55 kg|
|1 cubic centimeter||0.0353 oz||0.002205 lb||1 g||0.001 kg|
|1 cubic meter||35,274 oz||2,204.6 lb||1,000,000 g||1,000 kg|
The Temperature Affects the Weight of Water
As we mentioned briefly above, temperature has an effect on the density of water, and thus its precise weight will vary with the temperature. As the temperature of water rises, it expands, causing it to increase in volume slightly.
At a molecular level, as the temperature rises, the heat of the water molecules increases, which increases their energy. As the energy in the molecules rises, the particles within move and vibrate more, causing them to take up more space.
Thus, the warmer the water is, the more volume it will consume, and the lower its density will be. The chart below shows the density of water at various temperatures, according to the US Department of the Interior.
Density of Water at Various Temperatures
( °F / °C )
( grams per cm3 )
|32° / 0°||0.99987 g/cm3|
How Much Does a Gallon of Water Weigh?
We mentioned above that one gallon of water weighs 8.345 pounds at 39.2 °F when the density of water is exactly equal to 1.0 g/cm³. But, since the density of water fluctuates with the temperature, the weight of a gallon of water changes too.
So, just how much does a gallon of water weigh then? One gallon of water weighs between 8.288489 and 8.345404 pounds, depending on the temperature. The table below shows the weight at various temperatures.
( °F / °C )
|Weight of One Gallon of Water||Weight of Five Gallons of Water|
|32° / 0°||8.34432 lbs||41.721598 lbs|
|39.2°/4.0°||8.345404 lbs||41.72702 lbs|
|40°/4.4°||8.345321 lbs||41.726605 lbs|
|50°/10°||8.343318 lbs||41.71659 lbs|
|60°/15.6°||8.337643 lbs||41.688215 lbs|
|70°/21°||8.328881 lbs||41.64405 lbs|
|80°/26.7°||8.317781 lbs||41.588905 lbs|
|90°/32.2°||8.304512 lbs||41.52256 lbs|
|100°/37.8°||8.288489 lbs||41.442445 lbs|
How Much Does 5 Gallons of Water Weigh?
Trying to figure out how much a 5-gallon bucket of water weighs? At room temperature, five gallons of water weighs 41.64 pounds, but at 32.2 °F it weighs 41.727 pounds.
You can use the calculator or weight chart above for the full five-gallon weight range.
Working on a plumbing project? Use our pipe volume calculator to calculate the volume and weight of the water in your plumbing system.
How Much Does One Molecule of H2O Weigh?
In order to determine the weight of each H2O molecule, you need to first find its molar mass.
H2O Molar Mass
You can find molar mass of H2O by finding the mass of each element in the molecule and adding them together.
The mass of hydrogen is 1.00794 g/mol and oxygen is 15.9994 g/mol. Since it contains two hydrogen atoms and one oxygen atom, the molar mass formula for H2O is:
H2O molar mass = 1.00794 + 1.00794 + 15.9994
H2O molar mass = 18.01528
After finding the molar mass, you can find the weight of a molecule using Avogadro’s constant, which states that one mole is equal to 6.02214076 × 1023 elementary units of matter, such as a molecule. That’s a pretty big large number, so it’s typically represented using scientific notation.
Using this constant and the molar mass above, the formula to find the weight of one H2O molecule is:
H2O molecule weight = 18.01528/6.02214076 × 1023
H2O molecule weight = 2.9915 × 10-23 g
So, one molecule of H2O weighs 2.9915 × 10-23 grams.
- U.S. Department of the Interior, Bureau of Reclaimation, Ground Water Manual, from The Water Encyclopedia, Third Edition, Hydrologic Data and Internet Resources, 1977, Edited by Pedro Fierro, Jr.
and Evan K. Nyler, 2007, https://www.usbr.gov/tsc/techreferences/mands/mands-pdfs/GndWater.pdf
- U.S. Department of the Interior, US Geological Survey, Water Density, https://www.usgs.gov/special-topic/water-science-school/science/water-density
- National Center for Biotechnology Information, PubChem Compound Summary for CID 962, Water, 2021, https://pubchem.ncbi.nlm.nih.gov/compound/Water