How it's calculated
kilograms = US gallons × density(g/mL) × 3.785412
density in g/mL of the substance, 3.785412 = litres per US gallon. Reverse: gallons = kilograms ÷ (density × 3.785412).
Worked examples
| Liquid | kg per US gallon | Note |
|---|---|---|
| Water | 3.785 | Baseline |
| Gasoline | 2.86 | Lighter than water |
| Diesel | 3.22 | Denser than gas |
| Milk | 3.91 | Heavier than water |
Common questions
Which gallon does this use?
The US gallon of 3.78541 liters. The UK imperial gallon is larger, so it would give a heavier result.
Why does milk weigh more than water per gallon?
Milk is slightly denser because of dissolved fats, proteins, and sugars, so a gallon weighs a bit more than the same volume of water.