How much does a gallon of propane weigh?

Figures checked Nov. 10, 2026

A gallon of propane weighs about 4.24 pounds, from an answer in the customer questions on a propane retailer's product page; the same page's own description gives a slightly lower figure. We found no government page that gives one. Our converter uses the heavier figure, so it gives slightly fewer gallons per pound.

Amount	Propane
One gallon	about 4.24 lb
Full 20-lb cylinder	about 4.7 gallons
Full 30-lb cylinder	about 7 gallons
Full 100-lb cylinder	about 23 gallons

20 lb

4.7 gal

30 lb

7 gal

100 lb

23 gal

Gallons each cylinder holds when filled to its rated weight, from propane suppliers' published figures.

Propane pounds and gallons

The sums behind this tool are tested against 12 checks, including the limits where it gives no number.

Propane weight per gallon

The figure we use, about 4.24 pounds a gallon, comes from U-Haul's propane cylinder product page. The same page, and a county consumer protection column, give a slightly lower figure. We take the heavier one, because it gives fewer gallons from the same weight and so errs on the low side.

We looked for a figure from a government source and didn't find one. If you need an exact figure for a delivery or a dispute, ask your propane supplier or your state's weights and measures office.

Pounds to gallons, and gallons to pounds

To turn pounds into gallons, divide by 4.24. To turn gallons into pounds, multiply by 4.24. The converter above does both: gallons round down and pounds round up, so each answer leans the cautious way.

Small cylinders are sold by the weight of propane they hold, so this is how their gallons are worked out. Propane suppliers' charts give the round figures in the table above.

How to weigh a propane tank to see how much is left

This is for cylinders. For a big tank, read the gauge instead: the tank level page explains how.

Weigh the cylinder on a scale that reads in pounds.
Find the TW (tare weight) stamp on the cylinder. That is its empty weight.
Take the TW figure off the scale reading. What's left is the propane, in pounds.
Type the pounds into the converter above to see the gallons, or into the propane on hand calculator.

Propane Btu per gallon

The US Energy Information Administration (EIA) puts the heat in propane at about 91,450 Btu per gallon (91,452 on its Btu conversion page). Other official tables give 91,300.

Our cost and compare tools use EIA's figure. Our run-time calculator uses the lower one, so how long a tank lasts errs on the short side. To compare propane with other fuels by the cost of the same heat, use the fuel cost comparer.

Questions people ask

How much does a gallon of propane weigh?

About 4.24 pounds, from an answer on a propane retailer's product page; the page's own description gives a slightly lower figure. We found no government figure.

How many gallons are in a 20-lb propane tank?

About 4.7 gallons when it is filled to its full rated weight. Exchange cylinders often hold less.

How many Btu are in a gallon of propane?

About 91,450 Btu, by the EIA's figure. Other official tables give 91,300.

Before you light it

Carbon monoxide (CO) can kill. US Consumer Product Safety Commission (Official): “Fuel-burning heating systems, including furnaces and fireplaces, can produce CO, an odorless, colorless and deadly gas.” Source(opens in a new tab)
Fit CO alarms and test them. US Consumer Product Safety Commission (Official): “CO alarms should be placed on every level of the home and outside sleeping areas.” “Test the alarms every month to make sure they are working.” Source(opens in a new tab)
Have appliances checked every year. US Centers for Disease Control and Prevention (Official): “Have your heating system, water heater and any other gas, oil, or coal burning appliances serviced by a qualified technician every year.” Source(opens in a new tab)
Chimneys and vents too. US Fire Administration (Official): “Have chimneys and vents cleaned and inspected at least once a year.” Source(opens in a new tab)
If a CO alarm sounds (US: call 911): US Centers for Disease Control and Prevention (Official): “If the detector sounds leave your home immediately and call 911.” Source(opens in a new tab)
Know the signs. US Centers for Disease Control and Prevention (Official): “The most common symptoms of CO poisoning are headache, dizziness, weakness, nausea, vomiting, chest pain, and confusion.” Source(opens in a new tab)
Carbon monoxide (CO). CPSC (Official): "Fuel-burning heating systems, including furnaces and fireplaces, can produce CO, an odorless, colorless and deadly gas." "CO alarms should be placed on every level of the home and outside sleeping areas." Source(opens in a new tab)
If you smell gas (US: call 911). Connecticut Public Utilities Regulatory Authority (Official): "If the smell is strong or you are unsure, leave the building and then call." "Go to a phone that is not near the smell and call your propane company right away." "Don't smoke or strike any matches." "Don't flip light switches on or off." "Put out all open flames." "Call your propane company or 911 for help." This is general advice from one state's regulator: follow your own propane supplier's emergency instructions too. Source(opens in a new tab)
Keep propane cylinders outdoors. Utah State Fire Marshal (Official): "Never store a cylinder inside a house, building, or a garage." Source(opens in a new tab)
Outdoor-only heaters, grills and stoves stay outdoors. Mississippi State University Extension (Official), on outdoor-use-only heaters: "Never use them inside, even temporarily." Source(opens in a new tab)

Sources for this page

6 figures, each with its source

Every figure on this page, with its source. Open one to see the exact words on the source page and how it was checked.

Heat content of propane: 91,452 Btu per gallon Official
From US EIA Monthly Energy Review, Sept 2026, Appendix A Table A1 (Approximate Heat Content of Petroleum and Biofuels), which says: “Propane 3.841” Open the source (opens in a new tab)
Checked Nov. 10, 2026. A blind check looked it up again on Nov. 10, 2026 without seeing our figure: it found that our figure or its wording needed correcting, and the corrected version is the one shown.
Heat content of propane, for run times only (lowest official figure, kept as a safety margin): 91,300 Btu per gallon Official
From USDA Forest Service, Forest Products Laboratory: Fuel Value Calculator (updated July 2004), hosted by Nebraska Energy Office, which says: “Propane | gallon | 91,300 | 71,900 | 79%” Open the source (opens in a new tab)
Checked Nov. 10, 2026.
Gallons in a full 100 lb cylinder: 23 gallons Other source
From Ferrellgas (propane supplier): How to Choose the Right Propane Tank Size?, July 24 2025, which says: “100-lb: Holds 23 gallons of propane.” Open the source (opens in a new tab)
Checked Nov. 9, 2026. A second check re-opened the source page and matched it on Nov. 9, 2026.
Gallons in a full 20 lb cylinder: 4.7 gallons Other source
From Ferrellgas (propane supplier): How to Choose the Right Propane Tank Size?, July 24 2025, which says: “20-lb: Holds up to 4.7 gallons of propane.” Open the source (opens in a new tab)
Checked Nov. 10, 2026. A second check re-opened the source page and matched it on Nov. 9, 2026. A blind check looked it up again on Nov. 10, 2026 without seeing our figure: the two agreed.
Gallons in a full 30 lb cylinder: 7 gallons Other source
From Ferrellgas (propane supplier): How to Choose the Right Propane Tank Size?, July 24 2025, which says: “30-lb: Holds 7 gallons of propane.” Open the source (opens in a new tab)
Checked Nov. 9, 2026. A second check re-opened the source page and matched it on Nov. 9, 2026.
Weight of a gallon of propane: 4.24 pounds per gallon Other source
From U-Haul (retailer): 20-lb Steel Propane Tank product page (answer in the page's customer Q&A, 2021), which says: “The Propane that should be going into this tank only would weigh about 4.24lbs per gallon of propane.” Open the source (opens in a new tab)
Checked Nov. 10, 2026. A second check re-opened the source page and matched it on Nov. 9, 2026. A blind check looked it up again on Nov. 10, 2026 without seeing our figure: it didn't find a better source, so this figure stands.