Aviation Calculators

Trip fuel required calculator

Fuel required is flight time multiplied by fuel flow, plus whatever you decide to land with. The arithmetic is simple. Getting the units consistent is where it goes wrong.

Calculator

From your own aircraft manual, at the power setting you plan to use.
You choose this figure. No regulatory minimum is assumed.
You choose this figure. No regulatory minimum is assumed.
Fill in the fields and select Calculate. Your result appears here, with the assumptions that went into it.

This is an educational and planning aid. Use current official weather, your aircraft flight manual, and the rules that apply to your flight before you act on any figure here. See the aviation disclaimer.

What the result means

The total is the fuel you need on board before you start, broken down into trip fuel, reserve and anything extra you add for taxi, contingency or an alternate.

Every field on this page uses the single fuel unit you pick at the top. Nothing is converted behind the scenes, so litres can never be silently added to US gallons.

When this is useful

  • Before every flight, as the step between a planned route and a fuel order.
  • Checking whether a planned trip fits within the usable fuel your aircraft can carry.
  • Comparing the fuel needed for two different routes or two different cruise power settings.

How it is calculated

Trip fuel is fuel flow multiplied by planned time. The reserve can be entered either as a fixed quantity or as an amount of time at the same fuel flow, since both are common in practice. Anything extra is added on top.

No reserve is filled in for you. Reserve requirements vary by country, by whether the flight is VFR or IFR, and by the operation, so choosing one on your behalf would be wrong.

total fuel = (fuel flow x planned time) + reserve + extra

Worked example

Planned flight time
2 hours 30 minutes
Fuel flow
40 litres per hour
Reserve
45 minutes at the same flow

Trip fuel is 100 litres, the reserve is 30 litres, so 130 litres is needed on board.

Check: 2.5 hours at 40 litres per hour is 100 litres. 45 minutes is three quarters of an hour, so the reserve is three quarters of 40, which is 30 litres. The total of 130 litres follows directly.

Limitations

  • Fuel flow is not constant. The climb burns considerably more than the cruise, so a single cruise figure understates a flight with a long climb.
  • It uses the planned time, which assumes the planned groundspeed. A stronger headwind than forecast lengthens the flight and increases the fuel needed.
  • It does not know your aircraft usable fuel capacity, so it will happily return a figure larger than your tanks can hold.

Common mistakes

  • Mixing units. This page prevents it by using one selector for every field, but the fuel flow figure from your manual must be in that same unit.
  • Forgetting taxi and run up fuel, which on a short flight can be a noticeable fraction of the total.
  • Planning to the reserve. The reserve is what you land with, not something to dip into.

Sources

Related calculators

Calculation checked against the worked example above on 2026-09-23. How these are checked.