Gallons to Pounds
Is "A Pint a Pound"? (The World Around)
There is an old saying: "A pint's a pound, the world around."
This rhyme helped sailors and cooks estimate weight. Is it true? For Water, it is very close. A US pint of water weighs about 1.04 lbs. So, a gallon (8 pints) weighs about 8.34 lbs.
However, this saying fails immediately if you are measuring anything else. A pint of Molten Gold weighs 20 lbs. A pint of Gasoline weighs 0.75 lbs. You cannot convert Volume to Weight without knowing the substance's Density.
The Density Factor
Density describes how tightly packed the molecules in a liquid are. Our calculator uses this formula:
Weight = Volume × Density
If you fill a 5-gallon jerry can with Gasoline, it weighs about 30 lbs.
If you fill the same can with Water, it weighs about 42 lbs.
This difference matters if you are carrying the can a long distance!
US Gallon vs. Imperial (UK) Gallon
Another major source of confusion is the unit "Gallon."
- US Gallon (3.78 Liters): Used in the USA and parts of Latin America.
- Imperial Gallon (4.54 Liters): Used in the UK, Canada, and Caribbean.
Because the UK gallon is 20% larger, it naturally holds more weight.
- 1 US Gallon of Water = 8.34 lbs
- 1 UK Gallon of Water = 10.02 lbs
Common Liquid Weights (Cheat Sheet)
Here are the standard weights for common fluids (per US Gallon at room temperature).
| Substance | Density (lbs/gal) | Notes |
|---|---|---|
| Gasoline | 6.0 - 6.3 | Floats on water. Very light. |
| Alcohol (Ethanol) | 6.59 | Lighter than water. |
| Vegetable Oil | 7.6 - 7.7 | Floats on water. |
| Pure Water | 8.34 | The standard baseline. |
| Milk | 8.6 | Denser due to solids/fat. |
| Seawater | 8.55 | Denser due to salt. |
| Honey | 12.0 | Very dense sugar syrup. |
| Mercury | 113.0 | Liquid metal. Extremely heavy. |
Why Temperature Matters
Liquids expand when they get hot and contract when they get cold. This changes their density.
Example: A gallon of cold water weighs slightly more than a gallon of boiling water, because the boiling water has expanded and takes up more space (or conversely, fewer water molecules fit in the gallon bucket).
For most daily uses (cooking, carrying buckets), this difference is negligible. However, for industrial chemistry or buying fuel in bulk, temperature correction is mandatory.