How the distance is calculated
The calculator uses the haversine formula on a sphere with a mean radius of 6,371.0088 km. It converts both coordinates to radians, finds the central angle between them and multiplies by the radius.
The result is the shortest surface distance. A real flight follows a route shaped by airspace, weather and traffic, so the distance flown is usually longer.
Worked example
Heathrow at 51.4700 north, 0.4543 west and Kennedy at 40.6413 north, 73.7781 west are 5,540 km apart. That is 3,442 statute miles or 2,991 nautical miles, with an initial bearing of 287.9 degrees, which is west-north-west.
The bearing is the direction at the start of the route. On a long great-circle path the heading changes continuously, so the arrival heading is different.
Getting the coordinates
Decimal degrees are the easiest form: 51.4700, -0.4543 is Heathrow, with positive latitudes north and positive longitudes east. Degrees, minutes and seconds need converting first, and southern or western positions take a minus sign.
This page does not look up airport codes. Take the coordinates from an official aeronautical source or a map, because an airport's reference point and its runway thresholds are not the same place.
Limits of this calculator
It assumes a perfect sphere, which makes it accurate to roughly 0.5 per cent rather than to the metre. It does not model terrain, magnetic variation, airways or the earth's flattening.
For a time estimate from a distance, use the flight time calculator.
To turn a distance into an airborne time, use the US flight time calculator.
Inputs for the US flight distance calculator
Departure latitude
Decimal degrees, positive north of the equator. Heathrow is 51.4700.
Departure longitude
Decimal degrees, negative west of Greenwich. Heathrow is -0.4543.
Arrival latitude
Decimal degrees for the destination, positive north of the equator.
Arrival longitude
Decimal degrees for the destination, negative west of Greenwich.
CALCULATOR QUESTIONS
US flight distance calculator questions
Is this the same as the distance flown?
No. It is the shortest surface path. Airways, weather and airspace make the flown distance longer.
Why does the bearing change during the flight?
A great circle crosses meridians at different angles, so the heading you steer changes as you go.
Can I enter degrees, minutes and seconds?
Convert them to decimal degrees first: degrees plus minutes divided by 60 plus seconds divided by 3,600.
Does it work for driving distances?
Only as a straight-line measure. Road distance is longer and this page does not follow a network.