This calculator uses the spherical law of cosines, not the haversine formula.

Angles are converted from degrees to radians first, and the cosine input is clamped to keep `Math.acos` numerically stable.

Enter both latitude and longitude pairs in degrees, choose the output unit, and read the surface distance on the sphere.

1. Enter point 1 latitude and longitude.
2. Enter point 2 latitude and longitude.
3. Choose kilometers or miles.

New York City to London is a classic great-circle pair: the shortest surface route is about 5,570 km.

That is the distance along Earth’s surface, not a straight line through space.

The old copy said haversine, but the implementation was actually the spherical law of cosines. This version aligns the text with the code.

Latitudes outside -90 to 90 and longitudes outside -180 to 180 are rejected before the distance is computed.