Generator Fuel Runtime Calculator
Estimate a generator’s runtime using available fuel, consumption rate and a chosen reserve that should remain unused.
How to use this calculator
- Enter available fuel, fuel rate per hour and reserve percentage.
- Confirm that all inputs use the stated units and the same population, period or scope.
- Change one assumption at a time when comparing scenarios.
Formula used by the generator fuel runtime calculator
Hours = fuel × (1 − reserve%) ÷ litres/hour
- Hours = fuel × (1 − reserve%) ÷ litres/hour
- Fuel consumption changes with load and generator condition; use manufacturer data for the relevant operating point.
- Inputs are validated against required ranges and outputs are rounded for readability.
Worked examples
Worked example
25 litres available, 2.2 L/h consumption and 10% reserve.
Estimated usable runtime is about 10.23 hours.
Estimated usable runtime is about 10.23 hours.
Understanding the result
Estimate a generator’s runtime using available fuel, consumption rate and a chosen reserve that should remain unused.
Fuel consumption changes with load and generator condition; use manufacturer data for the relevant operating point.
Important notes
Fuel consumption changes with load and generator condition; use manufacturer data for the relevant operating point.
Use the result as a calculation aid for the inputs supplied; confirm critical specifications independently.
Frequently asked questions
Is fuel rate constant?
Usually not; load and operating conditions change consumption.
Does the estimate include refuelling?
No; it estimates one tank’s usable fuel.
How do I use this calculator?
Enter available fuel, fuel rate per hour and reserve percentage.
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Related explanations
Learn the method behind the number or compare the terminology before using the calculator.
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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.