Fuel Planning
Consumption, endurance, fuel remaining, trip fuel, reserve and segment planning; user assumptions, aircraft data and regulatory minimums are kept apart.
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Enter the cruise fuel flow (gal/h, or lb/h with a planning density), the usable fuel on board and the fuel burned before cruise (start, taxi, takeoff and climb). Give the trip as a direct time or as legs with distance and groundspeed — the same legs as the Time–Speed–Distance tool — add an alternate for IFR, and set your reserve in minutes. Choose which regulatory minimum to check: VFR day (30 min), VFR night (45 min) or IFR (45 min after the alternate).
The fuel bar lays the plan out in time at the cruise flow: allowance, trip legs, alternate and the reserve band, inside the bar of all usable fuel; the amber mark inside the reserve is the regulatory minimum, and anything beyond the end of the bar is a shortfall drawn in coral. Below it the fuel-remaining line falls from usable-minus-allowance to zero at the endurance, with a dot at every waypoint, the destination and the alternate; drag the amber cursor to read the fuel at any time.
The readout tags every number: [user] for your assumptions (flow, times, reserve minutes), [aircraft] for data read from the Cessna 172S POH when you select that preset (usable 53 gal, 1.4 gal start/taxi/takeoff, 6 lb/gal), [regulation] for the 14 CFR minimums. Endurance is shown both to dry tanks and until only the reserve remains; range is given with the reserve kept, and the dry-tank figure is labelled as something never to plan on.
Assumption: constant cruise flow for the whole trip and the alternate (climb and descent burn differently — put the climb fuel into the allowance from your POH climb table); planning densities (avgas 6.0, Jet A 6.8 lb/gal) are usual values, not measurements. The regulatory minimums are the legal floor, not a recommendation; the C172S numbers apply to that model only, and its cruise flow for your power setting must come from the POH cruise table (Figure 5-8), which this tool does not store.
Arithmetic: trip fuel = flow × trip time; alternate fuel = flow × time to the alternate; reserve fuel = flow × reserve minutes ÷ 60; required = allowance + trip + alternate + reserve; margin = usable − required; endurance = usable ÷ flow; time until only the reserve remains = (usable − allowance − reserve fuel) ÷ flow; range with the reserve = that time × groundspeed; fuel remaining at time t = usable − allowance − flow × t; lb ↔ gal through the selected density. Legs: time per leg = distance ÷ groundspeed, fuel at each waypoint from the cumulative time.
Regulation (summarised, not interpreted; the eCFR text is the authority): 14 CFR 91.151(a) — no flight in an airplane may begin under VFR conditions unless, considering wind and forecast weather conditions, there is enough fuel to fly to the first point of intended landing and, assuming normal cruising speed, to fly after that for at least 30 minutes during the day or 45 minutes at night ((b): rotorcraft 20 minutes). 14 CFR 91.167(a) — IFR: enough fuel to complete the flight to the first airport of intended landing, fly from there to the alternate, and fly after that for 45 minutes at normal cruising speed (helicopters 30); (b) the alternate is not required when a standard instrument approach exists there and the forecast from 1 hour before to 1 hour after the ETA is a ceiling of at least 2,000 ft above the airport elevation and visibility of at least 3 statute miles. Checked on 18 October 2026 against the eCFR (current to 15 October 2026).
Verified: the Cessna 172S POH section 5 sample problem (342 NM at 107 kt groundspeed, 8.9 gal/h → 28.5 gal cruise; 1.4 gal start/taxi/takeoff; 2.6 gal climb; 45-minute reserve 6.7 gal; total 39.2 of 53 gal usable) reproduced by the plan arithmetic; the E6-B instruction manual fuel problems (p. 12 / p. 37); PHAK ch. 10 planning densities; NIST gallon and pound definitions. Impossible plans (short of fuel, zero flow, a leg without groundspeed) are shown as such, never as an infinite endurance.
- 14 CFR § 91.151 Fuel requirements for flight in VFR conditions — (a)(1) 30 minutes by day, (a)(2) 45 minutes at night, (b) rotorcraft 20 minutes (binding regulation; text checked 2026-10-18 against the eCFR, current to 15 October 2026)
- 14 CFR § 91.167 Fuel requirements for flight in IFR conditions — (a) destination, alternate and 45 minutes at normal cruising speed (helicopters 30), (b) alternate waiver conditions (binding regulation; text checked 2026-10-18 against the eCFR, current to 15 October 2026)
- FAA Pilot’s Handbook of Aeronautical Knowledge, FAA-H-8083-25C (2023), ch. 10 Weight and Balance — planning fuel weights (avgas 6 lb/gal, Jet A 6.8 lb/gal, oil 7.5 lb/gal); ch. 16 Navigation — fuel consumption and flight planning
- Cessna Model 172S Information Manual 172SIM incorporating the Pilot’s Operating Handbook and FAA Approved Airplane Flight Manual, Revision 5 (19 July 2004), P/N 172SPHUS05 — Section 2 Fuel Limitations (56 gal total, 53.0 usable, 3.0 unusable), Section 5 Figure 5-7 note 1 (1.4 gal start, taxi and takeoff) and the sample problem (8.9 gal/h at 64 % power, 2.6 gal climb, 45-minute reserve 6.7 gal, 39.2 gal total), Section 6 (fuel at 6 lb/gal) — aircraft data, Model 172S only
- E6-B flight computer instruction manual, pp. 11–12 and 16 — fuel consumption problems and fuel weight (6 lb/gal), used as published test values
- NIST Special Publication 811 (2008), Appendix B — US gallon 3.785 411 784 L, pound 0.453 592 37 kg