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E6B Calc

Aviation fuel calculation: endurance, fuel required, reserve and point of no return

Fuel required is burn rate times leg time plus reserve. Endurance is fuel on board over burn rate. 48 US gallons at 10 gph, a 140-minute leg, a 45-minute reserve: you need 30.8 gal, land with 24.7 left, and could have stayed up 4 h 48 min total. The "remaining on arrival" number is worth checking every time — it's the one figure that makes a tight plan feel real rather than theoretical. E6B Calc's free Fuel screen handles it, and PNR & Equal Time Point covers the long legs.

3 min read · Updated 2026-09-11

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The aviation fuel calculation formula

  • Endurance (min) = fuel on board ÷ burn rate × 60.
  • Fuel for the leg = burn rate × leg time ÷ 60.
  • Fuel with reserve = burn rate × (leg time + reserve) ÷ 60.
  • Remaining on arrival = fuel on board − fuel for the leg.

Burn rate comes from the POH cruise tables, or better, from your own logs: fuel added divided by hours flown over a few fill-ups. The app takes burn rate as an input and won't reverse-engineer it from fuel used, so bring your own number.

Fuel required in E6B Calc

  1. On E6B, open Fuel under Planning.
  2. Enter Fuel on board and Burn rate in your chosen fuel unit.
  3. Enter the Leg time in minutes. Get it from Time · Speed · Distance if you only have distance and ground speed.
  4. Check the Reserve in minutes (it starts at 45) and set the one your rules and your own margins require.
  5. Read Endurance, Required with reserve, Required for the leg and Remaining on arrival. Not enough fuel appears when the leg plus reserve is more than you carry.
E6B Calc results; volumes to 1 decimal
InputUS gallonsLitres
Fuel on board48 gal150 L
Burn rate10 gph32 L/h
Leg time / reserve140 / 45 min210 / 45 min
Endurance4 h 48 min4 h 41 min
Required with reserve30.8 gal136.0 L
Required for the leg23.3 gal112.0 L
Remaining on arrival24.7 gal38.0 L

Fuel weight: gallons and litres to pounds and kilos

Weight and balance wants fuel as weight, not volume. Conversions > Fuel volume and weight: pick Avgas 100LL, Jet A or Mogas, type a volume. 40 US gallons of avgas comes to 151.4 L, 240 lb, 108.9 kg. 1,000 L of Jet A is 264.2 US gallons, 1,770 lb, 802.8 kg. One honest caveat: these run on fixed planning densities, 6.0 and 6.7 lb per US gallon, not the temperature-corrected figure your fuel supplier might actually use.

Point of no return and equal time point

Two numbers matter on a long leg over water or empty terrain. ETP is where pressing on and turning back take exactly the same time. PNR is the furthest point you can reach and still make it home on the fuel you're carrying. They're not the same question, which is easy to forget until you need both answers at once.

  • ETP distance = total distance × GS back ÷ (GS on + GS back).
  • PNR time = safe endurance × GS back ÷ (GS on + GS back); PNR distance = GS on × PNR time.
  1. Open PNR & Equal Time Point under Planning.
  2. Enter Total distance, Ground speed on and Ground speed back.
  3. Enter Safe endurance in minutes. As the app reminds you: Take the reserve out of the endurance first.
  4. Read Equal time point, Time to reach it, Then, either way, Point of no return and Time to the PNR.
300 nm leg, 120 kt on, 140 kt back, 180 min safe endurance
ResultValue
Equal time point161.5 nm from departure
Time to reach it1 h 21 min
Then, either way1 h 9 min
Point of no return193.8 nm from departure
Time to the PNR1 h 37 min

Headwind outbound pushes the ETP past the halfway mark, 161.5 of 300 nm, simply because the trip home is the faster leg.

Common mistakes

  • Planning with the POH burn rate at a lean mixture you never actually use. Your logs are more honest.
  • Forgetting taxi, run-up and climb fuel. Add them to the leg or to your margin.
  • Using total fuel instead of usable fuel as Fuel on board.
  • Leaving the reserve inside the endurance for a PNR calculation.

Questions and answers

How do I calculate fuel consumption in aviation?
Divide the fuel used by the flight time: 30 gallons over 3 hours is 10 gph. Use that figure as the Burn rate in the app.
Can I plan fuel in litres or imperial gallons?
Yes. Switch Fuel volume in Settings > Units of measurement; burn rate follows (L/h or imp gph).
What is the difference between ETP and PNR?
The ETP is about time: where continuing and returning take equally long. The PNR is about fuel: the last point from which you can still return.
Is the fuel calculator free?
Yes. Fuel, PNR & Equal Time Point and Conversions are free with no limits.

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