Propane Usage Calculator
A propane usage calculator converts the heat energy you need, measured in British thermal units, into gallons of propane. Propane has a well-established energy content: one US gallon of liquid propane contains about 91,500 BTU of heat. This tool takes the total BTU of heat required, whether for a heating season, a generator run, or an appliance, and divides by the energy content per gallon to return the gallons of propane that energy represents. The BTU figure is editable so you can model any load, and you can build it up from an appliance's BTU per hour rating multiplied by its run hours. Knowing the gallons helps you plan a tank fill, budget for delivery, or compare propane against natural gas, oil or electricity. Real appliances do not convert every BTU of fuel into useful heat, so for a net heating estimate you would divide by the appliance efficiency as well; this base tool reports the gallons of energy content before efficiency losses. The US Department of Energy publishes the energy content of fuels and home heating guidance. Every figure is computed deterministically from the formula shown below, with a worked example that reconciles exactly to the calculator so you can follow each step yourself.
Propane gallons divide the BTU needed by propane's energy content: gallons = BTU / 91,500. Needing 4,575,000 BTU of heat takes 50.00 gallons of propane. One gallon holds about 91,500 BTU.
Propane usage formula
Gallons = E / C
E = heat energy needed (BTU)
C = energy content of propane (about 91,500 BTU per gallon)
Each gallon of liquid propane holds about 91,500 BTU. Dividing the total BTU you need by that content gives the gallons of propane required, before appliance efficiency losses.
Worked example
A cabin needs 4,575,000 BTU of heat over a period, using propane at 91,500 BTU per gallon.
- Energy needed = 4,575,000 BTU
- Energy per gallon = 91,500 BTU
- Gallons = 4,575,000 / 91,500 = 50.00 gallons
The job needs 50.00 gallons of propane. These are the calculator's default inputs, so the result above matches the widget exactly.
Propane Usage Calculator: frequently asked questions
How many BTU are in a gallon of propane?
One US gallon of liquid propane contains about 91,500 BTU of heat energy. This is a standard value published by the US Department of Energy. Dividing the BTU you need by 91,500 gives the gallons of propane required to supply that much energy.
Does this account for appliance efficiency?
No. This base calculator converts BTU of energy directly to gallons of propane energy content. A real furnace or heater converts only part of the fuel into useful heat. To find the gallons actually burned, divide the result by the appliance efficiency (for example 0.90 for a 90 percent efficient unit).
How do I find the BTU I need?
Multiply an appliance's BTU per hour rating by the hours it runs. For a heating season, estimate the average BTU per hour and total hours, or work from past propane deliveries. Enter the resulting total BTU into the calculator.
How big a tank do I need?
A common residential tank holds 250, 500 or 1,000 gallons, though they are filled to about 80 percent for safety. Use the gallons from this calculator to judge how long a fill will last and how often you will need delivery.
Is propane cheaper than natural gas?
It depends on local prices. Propane holds more energy per gallon than a therm of natural gas, but the two are priced differently and compared on a cost-per-BTU basis. Use this calculator with a fuel cost comparison to weigh propane against natural gas, oil or electricity.
Official sources
- Fuel energy content and home heating guidance: US Department of Energy (DOE). As at 25 June 2026.
Reviewed by the CalculatorHub team, edited by James Graham, 25 June 2026. See our methodology. This is general information, not financial, tax, legal or investment advice.