Completing the fuel block on a flight plan means adding up burn for every leg and then layering on the regulatory reserves. This calculator does both: it works out time and fuel for each leg from distance, groundspeed, and burn rate, then sums the trip and adds taxi, reserve, alternate, and contingency allowances to give the total minimum fuel required on board.
How it works
For each leg the time and fuel are:
leg time (hr) = distance (nm) / groundspeed (kt)
leg fuel = leg time (hr) × burn rate (per hr)The trip fuel is the sum of all leg fuels. Reserve fuel is the reserve minutes expressed in hours multiplied by the cruise burn rate of the final (or a representative) leg. The total required fuel is:
total = taxi + trip + reserve + alternate + contingencywhere contingency can be entered as an absolute amount or computed as a percentage of trip fuel.
Example and tips
Three legs of 120 nm at 120 kt, 90 nm at 110 kt, and 60 nm at 100 kt, each burning 10 gph, give leg fuels of 10.0, 8.2, and 6.0 gallons — a trip total of 24.2 gallons. Add 1 gallon taxi, a 45-minute reserve (7.5 gallons), 5 gallons to the alternate, and 5 percent contingency, and the minimum fuel on board is about 38.9 gallons. Always cross-check the result against your aircraft’s usable fuel capacity — if the requirement exceeds capacity, the leg structure or the route needs to change.