Aircraft endurance calculator

Enter usable fuel, an expected hourly burn rate, and reserve minutes in consistent units. The result separates total endurance, reserve fuel, fuel available before the reserve begins, and practical flight endurance. It is a transparent planning calculation for quick comparisons and cross-checks, not a substitute for an approved flight manual, operating limitations, current conditions, or legally required preflight fuel planning.

Start with compatible fuel figures

This aircraft endurance calculator needs two fuel figures that use the same basis: usable fuel on board and fuel burned per hour. If usable fuel is entered in US gallons, the burn rate must be US gallons per hour; if fuel is measured by mass, both values must use kilograms or pounds. The selected unit labels the result but does not convert density, volume, or mass. Use usable fuel rather than total tank capacity, because unusable fuel is not available to sustain the engine and should not inflate the estimate. The hourly rate should also represent the operating condition you intend to assess. A cruise figure may be useful for a simple en-route comparison, but it does not automatically account for taxi, climb, descent, mixture changes, auxiliary equipment, multiple engines operated differently, or abnormal conditions. Confirm the figures against current aircraft documentation and your actual loading. Clear, compatible inputs make the arithmetic meaningful and prevent a plausible-looking answer from hiding a unit mismatch.

Understand how reserve changes endurance

The calculation first converts reserve minutes to hours and multiplies that duration by the entered hourly burn rate. That quantity becomes reserve fuel and is subtracted from usable fuel. The remainder is flight fuel available before the protected reserve would begin. Dividing flight fuel by hourly burn gives flight endurance, while dividing all usable fuel by the same rate gives total endurance if the reserve were included. Both values are shown so the effect of the reserve remains visible rather than being buried in one number. The method assumes a constant burn rate for the planned flight and reserve period. That is intentionally simple and reproducible, but real consumption changes with power setting, altitude, temperature, wind, aircraft configuration, engine condition, and flight phase. If required reserve fuel equals or exceeds usable fuel, the calculator rejects the input instead of returning zero or negative flight time. That warning means the entered fuel cannot support any planned flight duration while preserving the stated reserve under this model.

Use the result as a planning cross-check

Treat flight endurance as an arithmetic cross-check, not as an authorization to depart or continue a flight. A prudent workflow compares the result with a phase-by-phase fuel plan, weather and wind information, routing, alternate requirements, anticipated delays, and the applicable operating rules. Consider calculating more than one case: an expected burn rate, a conservative higher rate, and a longer reserve. Comparing those cases shows how sensitive available time is to assumptions and can reveal that a small change removes a meaningful safety margin. The result is rounded to six decimal places for stable API output; cockpit decisions should use appropriately conservative precision rather than treating extra decimals as accuracy. The API price is $0.002 per request, and the same deterministic calculation can be run in the browser. Neither route stores state, calls external services, or retrieves aircraft-specific performance data. Pilots and dispatchers remain responsible for selecting valid inputs, applying required regulations and procedures, and checking the final plan against approved sources for the particular aircraft and operation.