Flight Duration Calculator
The real time in the air between two local clock times in two different time zones, with the day change accounted for.
Results
What this tool does
A timetable tells you when a plane leaves in one city and when it arrives in another, and those two numbers are in different clocks. Subtracting them gives an answer that can be hours out, or negative. This page converts both to UTC first, so what comes back is the actual time you will spend in the seat — useful for comparing two itineraries, for judging whether a connection is realistic, and for knowing how much of the flight is worth sleeping through.
Formula
duration = arrival in UTC − departure in UTC (with the calendar day change included)
Variables
| Symbol | Meaning | Unit |
|---|---|---|
dep_time | Departure, local time | — |
dep_offset | Departure city, hours from UTC | h |
arr_time | Arrival, local time | — |
arr_offset | Arrival city, hours from UTC | h |
day_shift | Days later it lands | d |
OUT | Time in the air | — |
H | Flight time, hours | h |
MI | Flight time, minutes | min |
TD | Time difference between the cities | — |
DU | Departure in UTC | — |
AU | Arrival in UTC | — |
Worked example
- Departure, local time10:30
- Departure city, hours from UTC1 h
- Arrival, local time13:35
- Arrival city, hours from UTC-4 h
- Days later it lands0 d
- Time in the air8h05
- Flight time, hours8.08 h
- Flight time, minutes485 min
- Time difference between the cities-5h00
- Departure in UTC09:30
- Arrival in UTC17:35
Limitations
- Dates are handled as calendar dates. Time zones, daylight saving changes and public holidays are not taken into account.
Frequently asked questions
Why does a timetable say nine hours out and eleven back?
Two reasons, and this page separates them. The first is the time zones, which this calculation removes entirely by going through UTC — the clock difference is shown on its own line. What is left is real, and it is the jet stream: the high-altitude winds over the North Atlantic and the North Pacific blow west to east, so a westbound flight is pushing against a river of air that an eastbound one is riding.