Flight distance calculator

What the distance means

The number above is the length of the shortest path between two points on the Earth's surface, measured along a great circle. It is the same figure airlines and frequent-flyer programs call the "flight distance" or "great-circle miles", and it is shorter than the line you would draw between the same two points on a flat map. A route from New York JFK to London Heathrow covers 3,442 miles in a straight line over the planet, and the plane's heading changes from 51° at takeoff to 108° at landing because it follows the curve.

Besides the distance, the calculator gives the midpoint of the route. For JFK to LHR it lies at 52.22° N, 41.31° W, far above the latitude of either airport. On a flat map that point sits well north of the straight line between the two airports, which is how a great circle looks on most maps.

How it is calculated

The calculator uses the haversine formula: with latitudes φ₁ and φ₂ and longitudes λ₁ and λ₂, a = sin²(Δφ ÷ 2) + cos φ₁ · cos φ₂ · sin²(Δλ ÷ 2), and the distance is d = 2R · asin(√a). R is the IUGG mean Earth radius, 6,371.0088 km, which is (2a + b) ÷ 3 for the WGS 84 axes. The bearing at departure is atan2(sin Δλ · cos φ₂, cos φ₁ · sin φ₂ − sin φ₁ · cos φ₂ · cos Δλ). The final bearing is the reverse bearing plus 180°, and the midpoint comes from the standard vector form of the same geometry (Chris Veness, Movable Type Scripts). One mile is 1.609344 km and one nautical mile is exactly 1.852 km.

The flight time is our own arithmetic: route length (the great-circle distance times 1 plus your extension percentage) divided by speed, plus your extra minutes. Entering speed as a Mach number uses the speed of sound in the ICAO standard atmosphere above the tropopause, 573.6 knots (this is our derivation from the temperature of 216.65 K); Mach 0.80 then comes to 528 mph.

Worked example: Sydney to Los Angeles

Select SYD and LAX. The great circle is 7,494 miles (12,061 km) and the heading is 61° when leaving Sydney. At 500 mph that is 14 h 59 min of cruise. Add 5% for the real track and 30 minutes on the ground and in the climb and the answer is 16 h 14 min. Published schedules for this pair will differ from that, because airlines plan around winds and aircraft with different cruise speeds.

Limits of this method

First, the sphere. The Earth's equatorial radius is about 21 km larger than its polar radius, so spherical formulas are off by a fraction of a percent. Checked against the WGS 84 ellipsoid with Vincenty's method, the worst of all pairs among the 45 airports is Johannesburg to Cairo at 0.48%. For navigation or surveying use an ellipsoidal method.

Second, the route. Aircraft follow published airways and arrival and departure procedures, not a ruled line. EUROCONTROL tracks the gap as horizontal flight efficiency: the extra distance of the flown trajectory over the shortest path between its endpoints. Third, the speed. A jet's ground speed changes with altitude, weight and wind, and the airline's block time includes taxiing, holding and a margin. Use the calculator for a first idea of a trip, not to catch a connection.

Airport coordinates are the airport reference points from OurAirports, rounded to four decimals (about 10 meters), so the end of a runway can be a mile or two away; at flight distances this does not matter. For driving distance between two cities use the travel time calculator, for plain coordinates the coordinate distance calculator, and for what the time difference does to your body clock the jet lag calculator and the time zone converter.

Frequently asked questions

How far is New York from London by air?

From John F. Kennedy (JFK) to London Heathrow (LHR) the great-circle distance is 3,442 miles (5,540 km, 2,991 nautical miles). The route starts on a bearing of 51° (NE) and ends on 108°, because a great circle bends across the map. In the other direction, LHR to JFK, the distance is the same (3,442 miles) and the bearing at departure is 288°.

What is a great-circle distance?

It is the shortest path between two points along the surface of a sphere: a segment of the circle you get by slicing the Earth through its center and both points. On a flat map that path looks curved, which is why transatlantic routes arch toward the north. The calculator uses the haversine formula with the IUGG mean Earth radius, 6,371.0088 km.

How is flight time estimated here?

Cruise time is the distance divided by the speed you pick, plus the minutes you add for taxi, climb and approach. At 500 mph, JFK to LHR is 6 h 53 min of pure cruising; with 4% extra route length and 30 extra minutes it becomes 7 h 40 min. Wind, the route the airline files, air traffic control and the aircraft type all change the real number, so treat it as a planning estimate, not a schedule.

What speed should I enter?

Use the typical speed of the aircraft you expect, or switch the speed unit to Mach. In the International Standard Atmosphere the speed of sound at cruise altitude (above 36,089 ft) is 573.6 knots, so Mach 0.80 is about 459 knots or 528 mph true airspeed. This is our own conversion from the standard atmosphere. Real air is rarely standard, and the speed over the ground also depends on the wind, which adds to or takes away from the airspeed.

Why is the flight longer than the calculator's distance?

Airliners seldom fly the exact great circle: they follow published airways and procedures, and routes are shaped by traffic, restricted airspace and weather. EUROCONTROL defines horizontal flight efficiency as the comparison between the length of a trajectory and the shortest distance between its endpoints, expressed as a percentage of extra distance. The route-extension box in the calculator lets you add a percentage of your own; leave it at 0 for the pure geometric distance.

How accurate is the distance?

The Earth is slightly flattened, so a sphere is not exact. Compared with the WGS 84 ellipsoid (Vincenty's formula, which we used as a check), the spherical distance between any two of the 45 airports in the list is within 0.5%. The biggest gap is Johannesburg to Cairo, where the sphere gives 6,264 km against 6,234 km on the ellipsoid, 0.48% off. North-south routes show the largest error and east-west routes near the equator the smallest. Airline schedules use their own route lengths anyway.

Can I use any place on Earth, not only airports?

Yes. Choose Enter coordinates in either list and type decimal degrees: north and east are positive, south and west are negative, so Los Angeles is 34.05, -118.24. For ordinary distances between two coordinates without the flight-time part, the coordinate distance calculator does the same job.

Planning figures only; not for navigation or flight planning. Sources: Chris Veness, Calculate distance, bearing and more between latitude/longitude points (movable-type.co.uk); IUGG mean Earth radius R₁ = 6,371.0088 km; NIST SP 811, Appendix B.8 (mile and nautical mile); airport coordinates from OurAirports (public domain, airports.csv, October 27, 2026); ICAO standard atmosphere for the speed of sound; EUROCONTROL, horizontal flight efficiency (ansperformance.eu). How we check our calculators.