This site borrows heavily from http://www.movable-type.co.uk/scripts/latlong.html

This script calculates great-circle distances between the two points – that is, the shortest distance over the earth’s surface – using the ‘Haversine’ formula.

It assumes a spherical earth, ignoring ellipsoidal effects – which is accurate enough^* for most purposes… – giving an ‘as-the-crow-flies’ distance between the two points (ignoring any hills!).

Enter the co-ordinates into the text boxes to try it out. It accepts a variety of formats:

• deg-min-sec suffixed with N/S/E/W (e.g. 40°44′55″N, 73 59 11W), or
• signed decimal degrees without compass direction, where negative indicates west/south (e.g. 40.7486, -73.9864):