Skip to main content
Calculator Answers

Gallons to Pounds

Blake Boege
Written by Blake Boege · Founder, Calculator Answers

A volume-to-mass calculation utility that estimates the weight in pounds (lb) of a given volume of US gallons (gal). Because density depends on the liquid, this calculator assumes freshwater at standard temperature, noting that other substances (like oil, milk, or fuel) will have a different weight-to-volume ratio.

Convert gallons of water to pounds. This is a density calculation rather than a unit conversion, so the page assumes fresh water and shows what changes for milk, gasoline and other liquids.

See also: Pounds to Gallons, How Much Does a Gallon of Water Weigh, and Weight Converter.

Quick Answer

Convert liquid volume in gallons to weight in pounds. Under standard conditions, one US gallon of freshwater weighs approximately 8.345 pounds.

Direct Conversion

Gallons to Pounds

Bidirectional Gallons (gal) and Pounds (lb) Converter

Convert between gallons (gal) and pounds (lb) for fresh water.

Bidirectional live updates. Enter a number in either field to convert instantly.

Live Conversion

Answer

8.345 lb

1 gal = 8.345 lb

Formulalb = gal conversion
Gallons (gal)1 gal
Pounds (lb)8.345 lb

Gallons to Pounds Reference Table

Gallons (gal)Pounds (lb)Description
1 gal8.35 lbOne gallon of water
2 gal16.69 lbTwo gallons of water
5 gal41.73 lbOffice water cooler bottle
10 gal83.45 lbTen gallons of water
50 gal417.25 lbFifty gallons of water
Was this helpful?

Examples

1 gal

8.345 lb

How it works

Formula · lb = gal × 8.345 (fresh water near 39F) · gal = lb ÷ 8.345

To convert gallons (gal) to pounds (lb), perform the following calculation:

Formula

lb = gal × 8.345

Method

Multiply gallons by 8.345 to estimate the weight in pounds, assuming fresh water near 39F. Any other liquid, or warmer water, needs a different factor.

Understanding Gallons to Pounds Conversions

Converting a volume to a weight requires knowing the density of the liquid, so this page assumes fresh water and says so wherever it gives a number. One US gallon of fresh water weighs about 8.345 pounds when the water is cold, near 39F, where water is at its densest. Warm it to room temperature and the same gallon weighs about 8.33 pounds, because water expands as it warms. Heavier liquids such as milk or seawater weigh slightly more than water, while lighter ones such as gasoline or alcohol weigh considerably less.

Working it out by hand

The 8.345 is not arbitrary, and it is worth seeing where it comes from, because the chain is also where the assumptions live.

  1. A US liquid gallon is defined as 231 cubic inches, which works out at 3,785.411784 millilitres. That step is exact.
  2. Cold water, near 39F, has a density of very nearly 1 gram per millilitre. So the gallon holds about 3,785.4 grams, or 3.7854 kilograms. This step is where the substance and the temperature enter.
  3. A pound is 0.45359237 kilograms, so 3.7854 ÷ 0.45359237 = 8.345 pounds.

Only the first and third steps are definitions. The middle one is a physical measurement that depends on what the liquid is and how warm it is, and it is the reason this page is an estimate rather than a conversion. Change the liquid and only that step changes, but it changes the answer completely.

Common liquids, and how far they move the answer

Every figure below is one US gallon. The spread between the lightest and the heaviest is roughly two to one, which is the measure of how much the substance matters:

LiquidWeight per gallonAgainst water
Fresh water, 39F8.345 lbthe figure this page uses
Fresh water, 68F8.33 lbslightly lighter, water expands
Milkabout 8.6 lba little heavier
Seawaterabout 8.6 lba little heavier, from dissolved salt
Gasolineabout 6.1 lbmuch lighter, which is why it floats
Honeyabout 12 lbfar heavier

Those figures are approximate and vary with grade, temperature and composition. They are here to show the size of the error you would make by using the water factor on something that is not water, not to be converted from precisely.

Edge cases

  • This is not a unit conversion. Gallons measure volume and pounds measure weight. Moving between them needs a density, which is a physical fact about the substance, not a fixed ratio between the units.
  • The factor carries a temperature. 8.345 lb per gallon is water near 39F, where it is at its densest. Room-temperature water is about 8.33.
  • It is the US gallon. An Imperial gallon is about 20% larger, so a gallon of water weighs about 10 pounds under that definition.
  • Any other liquid needs a different factor. Using the water figure for gasoline overstates the weight by more than a third.
  • Dry ingredients are out of scope entirely. Flour and sugar settle and pack, so a weight has no fixed volume at all.

Sources, and what is not sourced

One step in the chain above rests on a definition and one does not, and it is worth saying which is which. The US liquid gallon is defined as 231 cubic inches, and the inch as exactly 2.54 cm, both recorded by NIST. The pound is defined as exactly 0.45359237 kilograms. Those two steps are exact.

The density of water is not a definition and is not cited here. It is a measured property that changes with temperature, and the 8.345 figure corresponds to water near its densest. Every weight on this page is therefore an estimate that inherits that assumption, which is why the page says fresh water wherever it gives a number rather than presenting the result as a conversion between units.

Your figures stay in the page

The values you enter are processed by this page in your browser. They are not sent to a server, not stored after you close the tab, and not visible to anyone else. There is no account and nothing to sign up for.

Related Conversion & Volume Calculators

Explore other related conversion calculators:

Pounds to GallonsHow Much Does a Gallon of Water WeighWeight ConverterLiters to Gallons

Related Calculators

More tools from Conversions

Pounds to GallonsConvert pounds to gallons. Find the direct volume answer for water, the conversion formula, standard reference tables, and a live converter.How Much Does a Gallon of Water WeighA US gallon of water weighs approximately 8.34 pounds (3.78 kg) at room temperature. An Imperial gallon weighs about 10.02 pounds. Compare weight and volume.Weight ConverterConvert weight and mass units: milligram, gram, kilogram, metric tonne, ounce, pound, stone, US ton, and imperial ton.Liters to GallonsConvert liters to gallons, in US liquid or Imperial units. Shows the formula, the substituted working, and a reference table for both standards.

Frequently asked questions

Multiply the gallons value by 8.345.

About 8.345 pounds, and that figure is for cold water. It corresponds to water near its densest, around 39F (4C). At ordinary room temperature, about 68F (20C), the same gallon weighs closer to 8.33 pounds, because water expands slightly as it warms.

No, density varies by substance. For example, a gallon of gasoline weighs around 6.1 pounds, while a gallon of heavy honey weighs about 12 pounds.

Fresh water, and nothing on this page works for anything else without changing the factor. Gallons measure volume and pounds measure weight, so converting between them is impossible without knowing what is in the container. Water is assumed because it is the common case, not because the arithmetic is general.

About 8.6 pounds. Milk is a little denser than water because of the sugars, proteins and minerals dissolved in it, so a gallon of milk outweighs a gallon of water by roughly a quarter of a pound.

About 6.1 pounds, which is roughly three quarters of what a gallon of water weighs. Gasoline is much less dense than water, which is also why it floats on it.

Because water expands as it warms, so the same gallon holds slightly less mass. Water is densest near 39F, where a gallon weighs 8.345 pounds. At 68F it is about 8.33 pounds, and near boiling it falls to roughly 8.04. The difference is small for everyday purposes, but it is why a single figure needs a temperature attached to it.

The US liquid gallon, which is 231 cubic inches or about 3.785 litres. An Imperial gallon is roughly 20% larger, at 4.54609 litres, so a gallon of water under that definition weighs about 10 pounds rather than 8.345.

No. Dry goods have their own densities and they settle and pack differently as well, so a weight of flour has no fixed volume. This page is for liquids, and for water specifically unless you substitute the factor yourself.

Multiply the gallons by that liquid's density relative to water, then by 8.345. Gasoline sits at roughly 0.74 times the density of water, so a gallon comes out near 6.1 pounds. You need a density figure for the specific liquid; there is no general rule.

About 41.7 pounds of water, plus the container. That is the figure behind office water coolers feeling heavier than people expect, and it is why the bottles are usually a two-hand lift.

About 8.6 pounds. Dissolved salt makes seawater roughly 2.5% denser than fresh water, so the difference is small per gallon but considerable across a tank.

Divide by the same factor instead of multiplying. The pounds to gallons page is set up for that direction and uses the identical 8.345 figure, so the two round-trip cleanly.

They are the same figure at different precisions. 8.345 is the cold-water value carried to three decimals, and 8.34 is that rounded. Given that the real answer moves with temperature and with whatever is dissolved in the water, three decimals is already finer than the assumption underneath it.

Coincidence, and a useful one. The old rule of thumb that a pint weighs a pound gives 8 pounds to the gallon, which is about 4% under the true figure. Close enough for a rough estimate, and wrong enough to matter when the quantity is large.