The Gas Cylinder Consumption Calculator helps you predict how long a pressurized gas cylinder will last based on your specific use. Whether you are using gas for an industrial process like welding or for a home appliance like a BBQ grill, this tool provides a reliable estimate of the cylinder's lifetime. By calculating the consumption rate, you can effectively plan your work, ensure you have enough gas to finish a job, and avoid running out unexpectedly.
formula
You can calculate a cylinder's lifetime using two different methods, depending on how the gas is consumed. One method applies to continuous flow applications, while the other is designed for appliances with a power rating.
For Continuous Flow Applications (e.g., Welding, Cutting, Purging)
This method calculates how long a cylinder will last when gas is used at a steady, known flow rate.
Primary Formula: Cylinder Lifetime
Formula:
Cylinder Lifetime (in minutes) = Total Usable Gas Volume / Flow Rate
Variables:
Total Usable Gas Volume: The total volume of gas the cylinder can deliver when expanded to atmospheric pressure.
Flow Rate: The rate at which your equipment uses gas, as set on your flowmeter or regulator. This must be in the same volume units as the Total Usable Gas Volume.
Supporting Formula: Total Usable Gas Volume
This formula calculates the volume of gas available from a high-pressure cylinder.
Formula:
Total Usable Gas Volume = Cylinder Water Capacity * (Cylinder Pressure / Atmospheric Pressure)
Variables:
Cylinder Water Capacity: The internal volume of the cylinder itself, often stamped on the cylinder neck.
Cylinder Pressure: The pressure of the full cylinder, read from its pressure gauge.
Atmospheric Pressure: The standard pressure of the air. Use 1 bar or 14.7 PSI. Ensure this is in the same unit as your Cylinder Pressure.
For Appliance-Based Consumption (e.g., BBQ, Heater, Stove)
This method is better for appliances like propane grills or heaters, where consumption is measured by the appliance's power rating.
Primary Formula: Cylinder Lifetime
Formula:
Cylinder Lifetime (in hours) = Total Energy in Cylinder / Appliance Power Rating
Variables:
Total Energy in Cylinder: The total amount of energy stored in the gas within the cylinder.
Appliance Power Rating: The energy consumption rate of your appliance when it is running. This is usually found on the appliance's specification label.
Supporting Formula: Total Energy in Cylinder
This formula calculates the total energy based on the weight and type of gas.
Formula:
Total Energy in Cylinder = Net Weight of Gas * Energy Content of Gas
Variables:
Net Weight of Gas: The weight of the gas inside the cylinder.
Energy Content of Gas: A standard value for the specific type of gas. For Propane, this is approximately 21,500 BTU per pound (lb). For Butane, it is approximately 21,200 BTU per pound (lb).
Helpful Unit Conversions
Pressure: 1 bar = 14.503 PSI
Volume: 1 cubic foot = 28.317 Liters
Weight: 1 kilogram = 2.2046 Pounds
Standard Propane BBQ Tank Runtime Estimates
This table provides a quick reference for how long a standard 20 lb propane tank will last with common BBQ grill power ratings.
| BBQ Grill Power Rating (BTU/hour) | Estimated Runtime (Hours) |
| 20,000 BTU/hour | 21.5 Hours |
| 30,000 BTU/hour | 14.3 Hours |
| 40,000 BTU/hour | 10.7 Hours |
| 50,000 BTU/hour | 8.6 Hours |
| 60,000 BTU/hour | 7.1 Hours |
Example
Let's calculate how long a standard backyard BBQ grill will run on a full propane tank.
Here is the information we will use:
Gas Cylinder: Standard 20 lb propane tank
Appliance: A BBQ grill with a power rating of 35,000 BTU/hour
First, you calculate the Total Energy in the Cylinder.
Total Energy in Cylinder = Net Weight of Gas * Energy Content of Gas
Total Energy in Cylinder = 20 lb * 21,500 BTU/lb = 430,000 BTU
Next, you use the primary formula to find the cylinder's lifetime.
Cylinder Lifetime (in hours) = Total Energy in Cylinder / Appliance Power Rating
Cylinder Lifetime (in hours) = 430,000 BTU / 35,000 BTU/hour = 12.28 hours
So, a full 20 lb propane tank will fuel the 35,000 BTU/hour grill for approximately 12.3 hours.
Most Common FAQs
Gases like propane and butane are stored as liquids under pressure and turn back into gas as you use them, a process called vaporization. This process requires heat from the surrounding environment. In cold weather, there is less ambient heat available, which slows down the rate of vaporization. This can reduce the pressure inside the cylinder, making it seem like it's running out of fuel faster or even stopping the flow of gas altogether, even when there is still liquid fuel inside.
For compressed gases like oxygen or argon, the pressure gauge gives a direct and accurate reading of how much gas is remaining. However, for liquefied gases like propane, this is not the case. The pressure inside a propane tank remains relatively constant as long as there is any liquid left to vaporize. The pressure will only begin to drop noticeably when the tank is nearly empty. Therefore, the most reliable way to know how much propane is left is by weighing the cylinder and subtracting its empty (tare) weight.
Both propane and butane are effective fuel gases, but their primary difference lies in their boiling points. Propane has a much lower boiling point (-44°F or -42°C) than butane (30°F or -1°C). This means propane will continue to vaporize and work effectively in very cold temperatures, making it suitable for all-season outdoor use. Butane, on the other hand, will stop vaporizing and will not flow out of the cylinder in freezing conditions, which limits its use to warmer climates or indoor applications.