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BIPM-ratified constants · v1.0

Converter

Gallons, to pounds converter calculator.

Convert gallons to pounds for any liquid. Supports US and UK gallons with built-in densities for water, fuel, milk, and more.

From

water

water

1 water =8.3454Pounds

Equivalents

Precision: 6 dp · Notation: Decimal · 2 units
US Gallon (3.785 L)us8.3454
UK / Imperial Gallon (4.546 L)uk10.0224

Common pairings

1 waterequals8.3454 us
1 waterequals10.0224 uk
1 milkequals8.5958 us
1 milkequals10.3231 uk
1 gasolineequals6.1547 us
1 gasolineequals7.3915 uk
1 dieselequals7.0936 us
1 dieselequals8.5191 uk

The conversion

How the value
is computed.

How to Convert Gallons to Pounds

Converting gallons to pounds requires knowing both the volume and the density (specific gravity) of the substance being measured. Volume alone does not determine weight — a gallon of gasoline weighs significantly less than a gallon of water or a gallon of milk. This gallons to pounds converter handles that calculation automatically for dozens of common substances.

The Core Formula

The gallons-to-pounds conversion formula is:

Pounds = Gallons × Specific Gravity × 8.345404

The constant 8.345404 represents the weight of one US gallon of pure water in pounds at 62°F (16.7°C). This value is derived from water's density of 1 kg/L combined with the US gallon volume of 3.785411784 liters, as established in NIST Special Publication 1038: The International System of Units (SI) Conversion Factors for General Use. Specific gravity (SG) is the dimensionless ratio of a substance's density to that of pure water at the same temperature.

Understanding the Variables

  • Gallons: The volume of liquid to convert. Enter any positive number of US or UK Imperial gallons.
  • Specific Gravity: The ratio of a substance's density to water's density. Water = 1.000. Values above 1.0 indicate a denser liquid; values below 1.0 indicate a lighter liquid.
  • Gallon Type: A US gallon equals 3.785 liters, while a UK Imperial gallon equals 4.546 liters — approximately 20.1% larger. For UK gallons, the water-weight constant becomes approximately 10.022 lbs per gallon.
  • Custom Specific Gravity: Enter a custom SG value (from a Safety Data Sheet or technical specification) to override the default for any unlisted substance.

US Gallon vs. UK Imperial Gallon

The US gallon (231 cubic inches) and the UK Imperial gallon (277.42 cubic inches) differ by about 20%. One Imperial gallon of water weighs approximately 10.022 lbs compared to 8.345 lbs for a US gallon. Always verify which gallon standard applies to a measurement before converting — fuel receipts, shipping manifests, and agricultural records may use either system depending on region.

Practical Applications and Importance

Gallons-to-pounds conversions are essential in numerous industries and everyday situations. In transportation and logistics, shipping companies must calculate the total weight of fuel tanks and liquid cargo to ensure vehicles stay within legal weight limits and comply with DOT regulations. In agriculture, farmers need accurate conversions when mixing pesticides, herbicides, and fertilizer solutions to ensure proper dosing rates and avoid crop damage. Food processing facilities convert liquid ingredient volumes to weights for recipe scaling and inventory management. Fuel stations and energy distributors use these conversions to reconcile inventory between volume measurements and weight-based billing systems. Environmental remediation specialists rely on precise conversions when calculating water treatment chemical dosages.

Common Substance Weights Per US Gallon

  • Water (SG 1.000): 8.345 lbs/gal
  • Seawater (SG 1.025): 8.554 lbs/gal
  • Whole Milk (SG 1.032): 8.612 lbs/gal
  • Motor Oil (SG 0.870): 7.260 lbs/gal
  • Diesel Fuel (SG 0.850): 7.093 lbs/gal
  • Jet Fuel / Kerosene (SG 0.800): 6.676 lbs/gal
  • Gasoline (SG 0.739): 6.167 lbs/gal

Fuel density values are sourced from the EPA Fuels and Oils Gallons to Pounds Conversion table, and energy unit standards are maintained by the U.S. Energy Information Administration (EIA) units and calculators reference. Agricultural liquid densities align with USDA ARS Measurement Conversion Tables.

Temperature Effects on Density

Density varies with temperature, which affects conversion accuracy. The standard reference temperature of 62°F (16.7°C) is used for most fuel and water density values. However, gasoline stored at 100°F may have a specific gravity approximately 2-3% lower than at 62°F, resulting in noticeable weight differences for large volumes. For critical applications in fuel quality testing or large-scale chemical processing, temperature-corrected density values should be obtained from current calibration data or the substance supplier.

Worked Examples

Example 1 — Water storage tank: A tank holds 50 US gallons of water. Pounds = 50 × 1.000 × 8.345404 = 417.27 lbs.

Example 2 — Vehicle fuel load: A truck carries 15 US gallons of gasoline (SG 0.739). Pounds = 15 × 0.739 × 8.345404 = 92.51 lbs.

Example 3 — UK gallon diesel conversion: Converting 10 Imperial gallons of diesel (SG 0.850). The UK water constant = 8.345404 × (4.546 ÷ 3.785) = 10.022. Pounds = 10 × 0.850 × 10.022 = 85.19 lbs.

Reference

Frequently asked questions

How many pounds is 1 gallon of water?
One US gallon of water weighs 8.345 pounds at standard conditions of 62 degrees F (16.7 degrees C). One UK Imperial gallon of water weighs approximately 10.022 pounds because the Imperial gallon holds 4.546 liters versus the US gallon's 3.785 liters, making the Imperial measure about 20.1% heavier for the same substance.
How many pounds does a gallon of gasoline weigh?
A US gallon of gasoline weighs approximately 6.167 pounds, based on an average specific gravity of 0.739. Actual weight varies by blend and temperature — winter-grade gasoline can weigh as little as 5.9 lbs per gallon while some summer blends reach 6.3 lbs per gallon. The EPA fuel conversion tables confirm this typical density range for petroleum gasoline.
What is the difference between converting US gallons and UK Imperial gallons to pounds?
A US gallon equals 3.785 liters and uses a water-weight constant of 8.345 lbs per gallon. A UK Imperial gallon equals 4.546 liters and uses a water-weight constant of approximately 10.022 lbs per gallon. For any given substance, converting UK Imperial gallons to pounds will always produce a result about 20.1% heavier than converting the same numeric volume in US gallons.
How do I convert 5 gallons of water to pounds?
Multiply 5 by the specific gravity of the substance and then by 8.345404. For water (SG 1.000): 5 times 1.000 times 8.345404 equals 41.73 lbs. For diesel (SG 0.850): 5 times 0.850 times 8.345404 equals 35.47 lbs. For whole milk (SG 1.032): 5 times 1.032 times 8.345404 equals 43.06 lbs. Always confirm the substance density before calculating.
Why does specific gravity matter when converting gallons to pounds?
Specific gravity measures how dense a liquid is relative to pure water. Because pounds express mass rather than volume, identical volumes of different liquids produce entirely different weights. Gasoline at SG 0.739 is about 26% lighter than water, while a heavy brine at SG 1.200 is 20% heavier. Omitting specific gravity in a gallons-to-pounds conversion introduces errors that matter in fuel loading, shipping weight limits, water treatment dosing, and agricultural spray calculations.
How many pounds is a gallon of diesel fuel?
A US gallon of diesel fuel weighs approximately 7.093 pounds, based on a typical specific gravity of 0.850. Ultra-low sulfur diesel (ULSD) spans a density range of roughly SG 0.820 to 0.870, placing its per-gallon weight between 6.843 and 7.260 lbs. Both the U.S. Energy Information Administration and EPA emissions reference materials use this density range for fuel weight and emissions factor calculations.