Gallons to Pounds Converter: The Weight of Water
Have you ever tried to lift a 5-gallon jug of water and been surprised by how heavy it is? Water is deceptively dense. Whether you are filling a fish tank on an upstairs floor, calculating the payload for a liquid tanker, or hiking with a hydration pack, knowing the weight of your water is essential. Our Gallons to Lbs Calculator provides an instant conversion based on the density of fresh water.
The Golden Number: 8.34
The standard conversion factor for fresh water at room temperature (70°F / 21°C) is:
- 1 US Gallon = 8.34 pounds (lbs)
This means a standard 5-gallon bucket of water weighs about 41.7 lbs (plus the weight of the bucket). A 50-gallon bathtub holds over 400 lbs of water.
Factors Affecting Weight
While 8.34 is the standard rule of thumb, the exact weight can fluctuate based on two main factors:
- Temperature: Water is densest at 39°F (4°C). As it heats up, it expands and becomes slightly lighter per gallon. Boiling water weighs about 8.00 lbs per gallon. Ice weighs even less (about 7.6 lbs per gallon equivalent) because water expands when it freezes.
- Salinity (Saltwater): Seawater is denser than fresh water because of the dissolved salt. A gallon of seawater weighs approximately 8.55 lbs. If you are calculating for a saltwater aquarium, add about 2.5% to the standard result.
Other Liquids
Important: This calculator is calibrated for Water. Other liquids have different densities (Specific Gravity).
- Gasoline: Much lighter than water (approx. 6.1 lbs/gallon).
- Diesel: Lighter than water (approx. 7.0 lbs/gallon).
- Milk: Slightly heavier than water (approx. 8.6 lbs/gallon).
- Concrete: Much heavier (approx. 20 - 24 lbs/gallon equivalent in fluid volume).
Conclusion
Never underestimate the weight of liquid. A filled 55-gallon drum weighs over 450 lbs—far too much for a single person to move safely without equipment. Use the Gallons to Lbs Calculator to plan your lifts, check your floor load limits, and ensure safe transport.