Verify before flight. Check the POH/AFM for aircraft-specific limits and performance.
Flight Planning
Endurance & Range Calculator
Estimate usable endurance and still-air/groundspeed range after reserve.
gal
gal/hr
kt
min
Usable endurance—
Maximum endurance—
Range after reserve—
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50 gallons with a 45-minute reserve
50 gal at 10 gal/hr gives 5 hours before reserve. Subtracting 45 minutes leaves 4.25 hours; at 120 kt groundspeed that is 510 NM.
This constant-flow estimate excludes separate taxi, climb and other allowances. The entered reserve is a planning assumption, not a determination of regulatory compliance.
Formula and method
Maximum endurance = usable fuel ÷ fuel flow. Reserve-adjusted endurance subtracts the entered reserve time before range is estimated from groundspeed.