Pilot tools
Airport distance calculator
Pick two airports to get the great-circle distance between them in nautical miles, kilometres and statute miles, the initial course, and the flight time at your groundspeed.
Sydney Kingsford Smith International Airport, Sydney (Mascot)
Melbourne Airport
Your average groundspeed, for the flight time
Great-circle distance
381nm
The straight-line great-circle distance. Real routes are usually longer.
- Kilometres
- 706km
- Statute miles
- 438mi
- Flight time
- ~51 min
- Initial course
- 232°true
Show calculationsHide calculations
Flying with Stratos? The tracking screen shows your distance to go, and its map draws your route, or a great-circle line between the airports without a SimBrief plan.
For flight simulation only. Don't use it for real-world flight planning or navigation.
How it works
The shortest path between two points on a sphere is part of a great circle, a circle around the Earth whose centre is the centre of the Earth. The calculator measures it with the haversine formula, from each airport's latitude and longitude, on a sphere with the Earth's mean radius of 6,371 km (3,440.065 nm).
a = sin²(Δlat ÷ 2) + cos(lat₁) × cos(lat₂) × sin²(Δlon ÷ 2)
distance (nm) = 2 × asin(√a) × 3,440.065
flight time = distance ÷ groundspeed
The airport positions come from OurAirports, a free public domain database of about 49,000 airports and seaplane bases, and the whole calculation runs in your browser. Search by ICAO code (YSSY), IATA code (SYD), name or town.
Great circle or the route you fly
The great-circle distance is the least you can fly between two airports. A real flight plan is longer: the departure and arrival procedures, the airways between them and any detours around restricted airspace or weather all add miles. Use the great circle to compare routes and pick an aircraft with the range, and your flight plan for fuel.
The flight time is the distance at your groundspeed, so it is the time in the air at cruise speed, not the scheduled time. Taxiing, the climb and the descent add to it. Our guide to block time and flight time explains the difference.
Questions
How is the distance between two airports measured?
Along the great circle between them: the shortest path over the Earth's surface, as if you stretched a string between the two airports on a globe. Aviation gives it in nautical miles. This calculator takes each airport's position from OurAirports and uses the haversine formula on a sphere with the Earth's mean radius of 6,371 km. Measuring on the slightly flattened shape of the real Earth changes the answer by about 0.5% at most.
Why is the distance I fly longer than the great-circle distance?
The great circle is the shortest possible path, and real routes rarely follow it exactly. Departures and arrivals follow published procedures, the route in between follows airways and waypoints, and flights go around restricted airspace and weather. On long flights, airlines also pick tracks that use the jet stream, which can be longer in distance but quicker in time.
How do you work out flight time from distance?
Divide the distance by your groundspeed. 381 nm at 450 kt is 0.85 hours, about 51 minutes. That is time at cruise speed over the great circle, so a real flight takes longer: taxiing, the climb and the descent are slower, and the route is usually longer. Groundspeed already includes the wind, so use the one you expect, not your airspeed.
Why does the shortest route look curved on a map?
Most flat maps, including most web maps, use the Mercator projection, which stretches distances more and more towards the poles. A great circle is straight on the globe, but on a Mercator map it bows towards the nearer pole. That is why a flight from London to Los Angeles passes over Greenland and Canada rather than across the middle of the Atlantic.
What is the difference between nautical miles and statute miles?
A nautical mile is exactly 1,852 m, based on one minute of latitude, which makes it easy to use with charts. A statute mile, the everyday mile, is 1,609.344 m. One nautical mile is about 1.151 statute miles or 1.852 km. Aviation and shipping measure distance in nautical miles and speed in knots, one nautical mile per hour.
What is the initial true course?
The direction you leave the departure airport on to follow the great circle, measured clockwise from true north. On a great circle the true course changes along the way, except when flying due north, due south or along the equator. Your compass and the sim show magnetic headings, which differ from true by the local magnetic variation.
Stratos by Skyvex Software
Free ACARS for every pilot.
On Windows, macOS and Linux.
Stratos reads Microsoft Flight Simulator and X-Plane directly. It tracks the whole flight from gate to gate, shows your distance to go on a live map, and files the PIREP before you leave the cockpit.