The measurement of a gallon is defined by its volume. Volume is the amount of space something takes up. A gallon of water and a gallon of honey will take up the same amount of space, but they will weigh different amounts. A gallon, therefore, does not have a definite weight, but its volume is exactly 3.78541 liters. We can use this information along with density to help find the weight of a gallon of water.
How much does Gallons of water weighs in KG?
Density is defined as the mass divided by volume. A substance with high density will have a lot of weight in a small volume. A great example of this is lead. Lead has a density of 11.34 grams per cubic centimeter.
Think of a cubic centimeter as a small block with a length, width, and height of 1 cm. That tiny block will weigh 11.34 grams. Now imagine that we increased the size of that cube to 1 meter in length, width, and height.
The new lead block will weigh 11,340 kilograms (12.5 tons). Let’s use a low-density example now. Grain alcohol has a density of 0.81 grams per cubic centimeter.
The same cubic centimeter will weigh 0.81 grams, and that same sized block that is 1 meter in length, width, and height will weigh 810 kilograms (just under 1 ton).
We know the density of various substances because of well known and documented measurements.
How to Calculate the Density?
In fact, you can easily test the density of objects with a scale and graduated cylinder. Simply fill a graduated cylinder partially with water. Note the volume and weight.
To learn the density of an object, add it to the graduated cylinder and simply mark its new volume and weight. (new weight minus old weight) divided by (new volume minus old volume). This can be done with any substance to find its density.
For water, its density is 0.997 grams per cubic centimeter. 1 milliliter is equivalent to 1 cubic centimeter, so water is also 0.997 grams per milliliter.
By using metric conversion rates, we also know that 1 liter is 997 grams. 1,000 milliliters in a liter, so 0.997 multiplied by 1,000 gives us 997 grams.
If every liter is 997 grams, then a gallon will be 3,774.05377 grams (a gallon is 3.78541 liters multiplied by 997 grams per liter). This is also 3.77 kilograms. In pounds, this makes 8.32 pounds. The weight of a gallon of water is 8.32 pounds.