Propane Tank Run Time Calculator

How it is calculated

The engine multiplies the weight of propane by its energy content, total BTU = lbs × 21,594, then divides by the appliance rating: hours = total BTU / BTU per hour. Days follow from days = hours / hours per day. The weight field is pounds of propane, not gallons and not the empty tank's weight, and the appliance rating is the BTU per hour printed on its label. Usage per day may be left empty or zero, in which case 24 hours is assumed and the days figure is the run time of continuous burning. Both the tank weight and the BTU rating must be above zero. The engine assumes the burner runs at its full rated output the whole time, so partly-lit burners or low settings last longer.

Common mistakes

• Entering the tank's nominal size when the tank is partly empty. The field takes the pounds of propane actually left; a 20 lb tank that is half full is 10 lb, and halves the 14.4 hours to 7.2.
• Entering gallons instead of pounds. Propane is entered by weight here, so a tank of 4.7 gallons must be converted to pounds first or the run time will be less than a quarter of the real value.
• Using the gross weight on the tank scale. The stamped tare weight of the empty cylinder is not propane, so subtract it to get the pounds of fuel inside.
• Using the maximum appliance rating for something that rarely runs full blast. A furnace or grill on low uses fewer BTU per hour, so this result is a lower bound on the burn time.
• Leaving hours per day empty and reading the days figure as real-world days. With 24 hours assumed, 0.6 days is only the non-stop figure, not how long a weekend grill tank will last.