The time–speed–distance relationship
Every E6B, every flight-computer app, and every paper nav log uses the same identity:
distance = speed × time
Pick consistent units — nautical miles with knots, statute miles with miles per hour, or kilometres with km/h — and you can solve for any one of the three. Enroute time (ETE) is what you add to a departure time to get an estimated time of arrival (ETA).
The speed in that equation is groundspeed. True airspeed ignores wind. Use the E6B wind triangle (and a TAS conversion if you started from the airspeed indicator) before you plan a leg. The resulting time also feeds the fuel planner and the top-of-descent calculator.
Worked examples
- 180 nm at 120 kt takes 1 hour 30 minutes. Departing at 09:00, ETA is 10:30.
- A 200 nm leg that must be flown in 1 hour 20 minutes requires 150 kt groundspeed.
- 45 minutes at 90 kt covers 67.5 nm.
- A 23:30 departure plus a 2-hour ETE arrives at 01:30 the next day.
How to use it
- Choose whether you want to solve for time, speed, or distance.
- Fill in the other two quantities and set the units to match your chart or GPS.
- Optionally enter a departure time to see the ETA.
Frequently asked questions
How do I calculate time, speed, or distance for a flight?
Distance = speed × time, with a consistent set of units. Time to fly a leg (ETE) is distance divided by groundspeed. Required speed is distance divided by the time you have. This page stores everything as knots, nautical miles, and hours, and converts what you type.
Should I use true airspeed or groundspeed?
Use groundspeed. True airspeed is the speed through the air; wind changes the speed over the ground. Get a groundspeed from the E6B wind triangle, a GPS, or a winds-aloft forecast before you solve for time or range.
How is ETA calculated?
ETA is departure time plus the enroute time. If that sum crosses midnight, the arrival is shown as the next day (or later, for very long times). The clock is a 24-hour clock and does not apply a time zone or daylight-saving change by itself.
Can I use statute miles and miles per hour?
Yes. Switch the distance unit to statute miles and the speed unit to mph (or km and km/h). The calculator converts internally so the relationship stays exact.