What does a gallons to pounds converter do?
It tells you what a gallon of something weighs. Type the number of gallons, pick the liquid, and the Gallons to Pounds Converter gives you the weight in pounds, plus kilograms and the answer for a UK gallon. A US gallon of water is 8.3454 lb. Five gallons is 41.727 lb. Twenty gallons is 166.91 lb.
Here's the part most converters skip. Gallons measure space. Pounds measure weight. The two only connect through density, which is how heavy a liquid is for its size. A gallon of gasoline weighs 6.18 lb. A gallon of honey weighs 11.85 lb. Same jug, almost twice the weight. Any page that gives you one gal to lb number without asking what's in the jug is quietly assuming water.
So this tool asks. It covers nine common liquids, takes a custom density for anything else, and shows the density it used with every answer. You can check the number instead of trusting it.
How to convert gallons to pounds
The formula is short:
pounds = gallons × pounds per gallon, and for any liquid, pounds per gallon = 8.3454 × density in g/mL.
The 8.3454 comes from two exact definitions. A US gallon is 3.785411784 liters. A pound is 0.45359237 kg. One liter of a liquid with a density of 1 g/mL has a mass of 1 kg, so a gallon of it is 3.785411784 ÷ 0.45359237 = 8.3454 lb. Every other liquid is that number scaled by its density.
Worked example: a full diesel tank
Say a pickup has a 26-gallon diesel tank and you want the fuel's weight for a payload check. Diesel is 0.85 g/mL in the converter.
- Pounds per gallon: 8.3454 × 0.85 = 7.0936 lb/gal.
- Weight: 26 × 7.0936 = 184.43 lb.
The converter shows the same line under the result, in the form 26 US gal × 7.0936 lb/gal (diesel) = 184.4335 lb. Tap Copy formula and you have the whole calculation for a note or a load sheet.
How much a gallon weighs, by liquid
These are the presets in the converter. Each row uses the same density the tool uses, at room temperature.
| Liquid | Density (g/mL) | lb per US gallon | lb per UK gallon |
|---|---|---|---|
| Water | 1.000 | 8.35 | 10.02 |
| Seawater | 1.025 | 8.55 | 10.27 |
| Milk (whole) | 1.03 | 8.60 | 10.32 |
| Gasoline | 0.74 | 6.18 | 7.42 |
| Diesel | 0.85 | 7.09 | 8.52 |
| Ethanol | 0.789 | 6.58 | 7.91 |
| Olive oil | 0.915 | 7.64 | 9.17 |
| Motor oil | 0.88 | 7.34 | 8.82 |
| Honey | 1.42 | 11.85 | 14.23 |
Not on the list? Pick Something else and type the density. Liquid propane is about 0.505 g/mL, which gives 4.21 lb per gallon, close to the 4.2 lb figure propane suppliers quote. Jet fuel (Jet A) runs about 0.80 g/mL, or 6.68 lb per gallon. Paint varies too much by product to give one number, so read the density off its safety data sheet.
Gallons of water to pounds
Water is the default and the most searched, so here's the table to keep. US gallons at the reference density of 1.000 g/mL:
| US gallons | Pounds | Kilograms | Where you meet it |
|---|---|---|---|
| ½ | 4.17 | 1.89 | Half-gallon jug |
| 1 | 8.35 | 3.79 | Gallon jug |
| 2 | 16.69 | 7.57 | Two jugs |
| 4 | 33.38 | 15.14 | Camping water container |
| 5 | 41.73 | 18.93 | Water cooler bottle, 5-gallon bucket |
| 6 | 50.07 | 22.71 | Large fermenting bucket |
| 10 | 83.45 | 37.85 | Small aquarium |
| 20 | 166.91 | 75.71 | Aquarium, RV fresh tank |
| 24 | 200.29 | 90.85 | 24 one-gallon jugs |
| 40 | 333.82 | 151.42 | Water heater |
| 55 | 459.00 | 208.20 | Steel drum, rain barrel |
| 100 | 834.54 | 378.54 | Large stock tank |
| 275 | 2,294.99 | 1,040.99 | IBC tote |
None of these include the container. A 5-gallon water cooler bottle full of water is over 40 lb before you count the plastic, which is why it's a two-hand lift.
8.34 or 8.35? Both are right for different water. 8.3454 lb is water at its reference density of 1 g/mL, which is what pure water hits at about 4 °C (39 °F). Cool tap water around 60 °F is about 8.34 lb. Warm water at 70 °F is about 8.33 lb. For anything outside a lab, the gap doesn't matter.
US gallons vs UK gallons
A UK imperial gallon is 4.54609 liters. A US gallon is 3.785411784 liters. The imperial one is about 20% bigger, so it holds about 20% more weight of any liquid. An imperial gallon of water weighs 10.02 lb, and that's no accident. When Britain set the imperial gallon in 1824, it defined it as the volume of 10 pounds of water.
The converter answers both every time. The US figure leads. If you type 5 UK gal or 5 imperial gallons, the imperial answer moves to the top instead. Use the imperial line for British boats and caravans, and for older Canadian manuals and fuel figures.
Where people get gallon weights wrong
Using water's number for everything. 8.34 lb per gallon is only right for water. For 15 gallons of gasoline, using the water figure gives 125 lb when the real answer is 92.6 lb. That's a 32 lb error in a fuel load.
Mixing up US and UK gallons. A 20% error is big enough to matter on a trailer or a boat. If the source is British, or a Canadian manual from before metric, check which gallon it means.
Forgetting temperature. Liquids expand as they warm. Water barely moves at normal temperatures, but gasoline expands about 0.1% for every °C. That's why fuel is often sold by volume corrected to a reference temperature. For a home calculation, the room-temperature values here are close enough.
Weighing solids by the gallon. A gallon of sand weighs much less than a gallon of solid stone, because a poured pile is part air. For solids, use the bulk density (the weight of the material as it sits in a bucket) in the custom density field.
Related converters
If you need volume and not weight, Gallons to Liters converts between the two volume units directly. To turn the pounds you get here into metric, use lbs to kg, or lbs to oz for small amounts. For kitchen amounts by ingredient, Cups to Pounds knows flour, sugar and butter. If you know a mass and a volume and need the density itself, the Density Calculator solves for it.
Frequently asked questions
How many pounds is a gallon?
It depends on the liquid. A US gallon of water is 8.35 lb (8.3454 at a density of 1 g/mL). A gallon of gasoline is about 6.18 lb, milk about 8.60 lb, and honey about 11.85 lb. Gallons measure volume, so the weight always depends on what fills the gallon.
How much does a gallon of gas weigh?
About 6.18 lb per US gallon, using a gasoline density of 0.74 g/mL. Pump gasoline ranges from roughly 6.0 to 6.5 lb per gallon depending on the blend, ethanol content and temperature. Diesel is heavier at about 7.09 lb per gallon.
How much do 5 gallons of water weigh?
41.73 lb in US gallons, plus the container. In UK imperial gallons it's 50.11 lb. That's the weight of a standard water cooler bottle's contents.
How do I convert pounds back to gallons?
Divide by the liquid's pounds per gallon. 100 lb of water is 100 ÷ 8.3454 = 11.98 US gallons. For gasoline, divide by 6.1756 instead. The table above gives the figure for each preset liquid.
Can I type a fraction?
Yes. The Gallons to Pounds Converter reads 1/2, 1 1/2, 1½, decimals like 2.5, grouped numbers like 1,000, and a trailing gal or gallons.
Where do I find a liquid's density?
On its safety data sheet, listed as density or specific gravity. Values in g/cm³, kg/L and g/mL are all the same number, and specific gravity for a liquid is the same number again. Type it into the custom density field.