Gas Cylinder Runtime Calculator
This calculator converts the entered gas mass and assumed energy content into usable energy, then divides by an appliance’s useful output demand to estimate runtime. It is a planning estimate, not a safety assessment.
How to use this calculator
- Enter net fuel mass, an appropriate energy-content assumption and useful output demand.
- Check that units, denominator definitions and time periods are consistent before comparing scenarios.
- Run a second scenario when an assumption is uncertain.
Formula used by gas cylinder runtime calculator calculator
Fuel energy (kWh) = net fuel mass (kg) × energy content (MJ/kg) / 3.6; useful runtime = fuel energy × efficiency / appliance output power.
- Fuel energy (kWh) = net fuel mass (kg) × energy content (MJ/kg) / 3.6; useful runtime = fuel energy × efficiency / appliance output power.
- Actual fuel usage varies. Follow cylinder, regulator and appliance instructions; never operate fuel-burning appliances indoors unless they are explicitly designed and approved for that use.
- The tool performs arithmetic on the values entered and does not validate assumptions against outside records.
Worked examples
Worked example
11 kg of fuel at 46 MJ/kg, 2 kW useful demand and 90% effective delivery.
Fuel energy ≈ 140.6 kWh; useful energy ≈ 126.5 kWh; runtime ≈ 63.2 hours.
Estimated runtime is based on the entered fuel energy and useful power demand.
Understanding the result
This calculator converts the entered gas mass and assumed energy content into usable energy, then divides by an appliance’s useful output demand to estimate runtime. It is a planning estimate, not a safety assessment.
Actual fuel usage varies. Follow cylinder, regulator and appliance instructions; never operate fuel-burning appliances indoors unless they are explicitly designed and approved for that use.
Important notes
Actual fuel usage varies. Follow cylinder, regulator and appliance instructions; never operate fuel-burning appliances indoors unless they are explicitly designed and approved for that use.
Treat this output as an estimate tied to the stated inputs. For regulated, safety-critical, tax or professional decisions, verify applicable official guidance and specifications.
Frequently asked questions
Is this suitable for life-safety planning?
No. Use manufacturer runtime data and maintain safe reserves.
Does it include a reserve?
No. The theoretical estimate assumes the entered usable gas mass is available.
How should I interpret the result?
Actual fuel usage varies. Follow cylinder, regulator and appliance instructions; never operate fuel-burning appliances indoors unless they are explicitly designed and approved for that use.
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This page provides a calculation tool plus explanatory information so you can understand what the result means and when the underlying method may not fit your situation.