Point of No Return Calculator
On a long over-water or remote leg with no alternate ahead, the point of no return is the last position from which the aircraft can still get back to its departure airfield within its safe endurance. Past it, turning back is no longer possible on the fuel remaining. The classic formula balances the outbound and return times against the fixed endurance, accounting for wind making one leg faster than the other. This calculator takes your safe endurance and the outbound and return ground speeds and returns the time and distance to the point of no return. Enter endurance after subtracting required reserves.
Point of no return formula
Time to PNR = endurance * return GS / (outbound GS + return GS)
Distance to PNR = time to PNR * outbound GS
Return time from PNR = distance to PNR / return GS
Time to PNR (min) = time to PNR (hr) * 60
The outbound and return times together equal the endurance. Because wind makes the legs unequal, the slower return leg pulls the point of no return closer to the departure point.
Point of no return notes
- Use safe endurance after subtracting required reserves, so the reserve survives the return.
- The PNR matters most when no usable alternate lies ahead on the route.
- A slower return ground speed, from a headwind home, moves the PNR closer to departure.
- Recompute in flight if winds or fuel flow differ from the planning figures.
- The point of no return is distinct from the equal time point, which ignores endurance.
Point of no return: frequently asked questions
What is the point of no return?
The point of no return, or PNR, is the farthest point along a route from which the aircraft can still return to its departure point within its safe endurance. Beyond it there is not enough fuel to turn back. It matters when no suitable alternate lies ahead, such as long over-water or remote legs.
How is the time to the point of no return calculated?
Time to the PNR equals the safe endurance multiplied by the return ground speed, divided by the sum of the outbound and return ground speeds. The distance is that time multiplied by the outbound ground speed. The asymmetry comes from wind making the outbound and return legs take different times.
Why do outbound and return ground speeds differ?
Wind helps in one direction and hinders in the other. A tailwind outbound becomes a headwind on return, so the same air distance takes longer coming back. Because endurance is fixed by fuel, the PNR shifts toward the departure point when the return leg is slower than the outbound leg.
What endurance figure should I use?
Use safe endurance: the total flight time available on usable fuel after subtracting your required reserves. Never include reserve fuel in the endurance you enter here, because the PNR must leave the reserve intact on arrival back at the departure airfield.
How does the PNR differ from the equal time point?
The equal time point is where the time to continue to the destination equals the time to return, and it does not depend on endurance. The point of no return depends on how much fuel, and therefore endurance, you have. They coincide only in special cases and are computed differently.
Official sources
- FAA: Pilot's Handbook of Aeronautical Knowledge.
- U.S. Electronic Code of Federal Regulations: 14 CFR fuel reserve requirements.
Reviewed by the CalculatorHub team, edited by James Graham, 17 June 2026. See our methodology.