Straight-Line Distance vs Driving Distance

The distance between two points depends on the path you choose. A line on a globe, a road journey and a walk can all have different lengths. Understanding the calculation prevents a useful estimate from becoming a misleading travel plan.

Great-circle distance

Our calculator uses the haversine formula to estimate the shorter arc between two coordinates on a spherical Earth. The calculation uses a mean Earth radius of 6,371 kilometres. The result is commonly called an as-the-crow-flies distance.

Why roads can be longer

Road routes follow available streets and crossings. Rivers, restricted areas, mountain passes, one-way streets and bridges can add distance. Two places on opposite sides of a river might be close on a map but far apart by road.

Distance does not tell you travel time

A short route can take longer than a long one because of congestion, road quality, transfers or speed limits. Our result includes no live traffic, elevation model, ferry schedule or routing data. Use a route planner for a real journey.

Worked example

Enter London as 51.5074, −0.1278 and Paris as 48.8566, 2.3522. The spherical great-circle result is roughly 344 kilometres, or about 214 miles. That number is not the length of a driving itinerary between the cities.

Unit choices

The tool offers kilometres, miles and nautical miles. A mile is 1.609344 kilometres; a nautical mile is 1.852 kilometres. Changing the unit changes the displayed number, not the pair of places or the underlying distance.

Limitations

Earth is not a perfect sphere, and height differences are not included. Small rounding and measurement differences can affect results. The tool is intended for general comparisons and learning, not surveying, aviation or safety-critical navigation.