Where do I find the tare weight?

The tare weight is stamped near the tank handle or collar, marked TW followed by a number in pounds. A standard 20 lb BBQ tank typically has a tare of 17 to 18 lb when empty.

Why is a "20 lb" tank only filled to 20 pounds of propane?

Tanks are filled to about 80% of liquid capacity to leave room for vapor expansion as temperature rises. A 20 lb tank is rated to hold 20 lb (about 4.7 gallons) of propane at that safe fill level.

Does temperature affect how long propane lasts?

The energy stored does not change, but very cold weather lowers tank pressure and can reduce the flow to high-demand appliances. The burn-time estimate assumes the appliance runs at its rated BTU draw.

How do I find my appliance BTU rating?

Check the appliance label or manual. A typical gas grill burner runs 20,000 to 40,000 BTU/hr, a patio heater around 40,000, and a tankless setup far more. Enter the combined rate of whatever you run.

Propane Tank Usage Calculator

Current Gross Weight (lb)

Empty Tare Weight (lb)

Rated Full Propane Weight (lb)

Appliance Burn Rate (BTU/hr)

The tare weight (TW) is stamped on the tank collar. A standard BBQ tank holds 20 lb of propane.

Burn Time14.4 hr

Propane Remaining100%

Gallons Remaining4.72

Energy Remaining (BTU)431,604

A propane tank has no fuel gauge, but its weight tells you exactly how much is left. Liquid propane weighs about 4.24 pounds per gallon and carries roughly 91,500 BTU per gallon. This tool subtracts the stamped empty (tare) weight from the current weight to find the propane remaining, converts that to gallons and energy, and divides by your appliance burn rate to estimate run time.

Formula

hours = ((gross - tare) / 4.24 x 91,500) / BTUhr

gross: Current total tank weight, lb
tare: Empty tank weight (TW stamp), lb
4.24: Pounds of propane per US gallon
91,500: BTU of energy per gallon of propane
BTUhr: Appliance consumption rate, BTU per hour

How it works

Weigh the tank and enter the gross weight, then enter the tare weight (TW) stamped on the collar and the tank rated full propane weight (20 lb for a standard grill tank).
Propane weight = gross minus tare; gallons = that weight divided by 4.24 lb per gallon; energy = gallons times 91,500 BTU.
Burn time = total BTU divided by your appliance burn rate in BTU per hour, and percent remaining compares propane weight to the rated full weight.

Worked example

A full 20 lb grill tank (37.5 lb gross, 17.5 lb tare) running a 30,000 BTU/hr burner.

Propane = 37.5 - 17.5 = 20 lb, which is 20 / 4.24 = 4.72 gallons.
Energy = 4.72 x 91,500 = about 431,600 BTU.
Burn time = 431,600 / 30,000 = about 14.4 hours.

About 14.4 hours of run time at 100% full.

Frequently asked questions

Where do I find the tare weight?: The tare weight is stamped near the tank handle or collar, marked TW followed by a number in pounds. A standard 20 lb BBQ tank typically has a tare of 17 to 18 lb when empty.
Why is a "20 lb" tank only filled to 20 pounds of propane?: Tanks are filled to about 80% of liquid capacity to leave room for vapor expansion as temperature rises. A 20 lb tank is rated to hold 20 lb (about 4.7 gallons) of propane at that safe fill level.
Does temperature affect how long propane lasts?: The energy stored does not change, but very cold weather lowers tank pressure and can reduce the flow to high-demand appliances. The burn-time estimate assumes the appliance runs at its rated BTU draw.
How do I find my appliance BTU rating?: Check the appliance label or manual. A typical gas grill burner runs 20,000 to 40,000 BTU/hr, a patio heater around 40,000, and a tankless setup far more. Enter the combined rate of whatever you run.

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