Every liquid has its own weight

Gallons to pounds calculator

Choose your liquid and gallon type. Get an instant weight, see the density behind it, and convert a whole batch when you need to.

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Water at 70°F / 21°C

USGS table density: 0.99802 kg/L. Dissolved substances can change this value.

View the density source

Uses the listed USGS density, with no interpolation. Choosing a temperature restores the table value.

Edit density & record your assumptions

Editing density overrides the preset. For liquids other than water, use a measured density at your temperature; no automatic temperature correction is applied.

Your liquid weighs
41.6444
pounds

5 US gallons of water at 70°F / 21°C.

1 US gallon ≈ 8.32888 lbUsing a density of 0.99802 kg/L
18.92706 LEquivalent liquid volume
18.88958 kgEquivalent liquid mass
The calculation5 × 3.785411784 L/US gal × 0.99802 kg/L ÷ 0.45359237 kg/lb

Water density is a table estimate at the selected temperature. Extra displayed digits do not guarantee measurement accuracy.

Liquid only. Container weight is excluded. For solutions, this is the mass of the entire solution, not the mass of one active ingredient.

One liquid. A whole list.

Convert multiple amounts using the liquid, density and units selected above. Keep the output as a table or download it.

One amount per line, or separate with commas or semicolons. Use decimal points and no thousands separators. Up to 100 amounts.

US gallonsPounds

How much does a gallon weigh?

One US liquid gallon for each reference liquid. Each row uses its own stated temperature—not one shared temperature.

LiquidDensity · kg/Llb / US galReference temperature
Water0.998028.3288870°F / 21°C
Milk1.0318.6041159°F / 15°C
Soybean oil0.917.5943277°F / 25°C
Gasoline0.756.2590559°F / 15°C
Diesel fuel0.847.0101459°F / 15°C

Reference estimates only. Milk and fuel presets use the midpoint of the cited density range. Oil and chemical values describe the cited products. Custom edits affect your calculation, not this reference table.

A simple relationship

How to convert gallons to pounds

Gallons tell you how much space a liquid takes up. Pounds tell you its mass. Density connects the two, so a gallon of water and a gallon of oil need different conversion factors.

Pounds = gallons × liters per gallon × kg per liter ÷ 0.45359237Use 3.785411784 liters for a US liquid gallon or 4.54609 liters for an Imperial gallon.

For example, 5 US gallons of water at the 70°F / 21°C table reference weighs approximately 41.644 pounds. Five Imperial gallons of the same water weighs approximately 50.013 pounds. The liquid is the same; the gallon definition changes the volume.

For pounds to gallons, reverse the relationship: multiply pounds by 0.45359237, divide by density in kg/L, then divide by liters per gallon.

The details that matter

Use the density of your actual liquid

Composition and temperature can both change density. A fuel blend may differ from another fuel, and a milk sample may differ with its fat and solids content. A general preset is a starting point, while a measured product density gives a closer match.

Water has selectable temperature references from the USGS table. Other presets retain their published temperature assumptions. We do not apply a water-based correction to oils, milk or fuels.

The result is the mass of the full liquid or solution. To find an ingredient's mass in a solution, you also need its concentration and whether that concentration is defined by mass or volume. A percentage alone does not tell the whole story.

Common conversion questions

Is one gallon always 8.34 pounds?

No. That is a familiar approximation for a US gallon of water under certain conditions. It is not a fixed volume-to-mass conversion. The liquid, temperature and gallon definition all matter.

Which gallon should I select?

Choose US gallons for a US liquid measure. Select Imperial gallons when that is the stated measurement. One Imperial gallon is about 20.1% larger than one US liquid gallon. This tool does not use the US dry gallon.

Can I use a density from a safety data sheet?

Yes. Enter the density and matching unit from the product sheet, and record its temperature and formulation. Relative density or specific gravity is not a density unit by itself; it needs its reference-water density and temperature before conversion to kg/L.

Does changing temperature change the liquid's mass?

For a fixed amount of liquid with no loss or gain, mass stays the same while its volume can change. This tool calculates the mass of the volume you enter at the selected or recorded density.

Why is the result shown as an estimate?

The unit conversions are defined, but a preset density may not exactly describe your sample. Source ranges are reference ranges, not guaranteed bounds. More decimal places in a calculation cannot make a measurement more precise.

Where do my saved settings go?

Only into this browser's local storage when you choose Remember my settings. Calculations and notes are not sent to a server. Reset removes the saved settings. CSV and copied results let you keep a separate record.

Density sources & unit definitions

Reference data checked September 2026. Source names identify the reference only; no affiliation or endorsement is implied.