📏 Distance Calculator
Enter the latitude and longitude of two points to get the great-circle distance between them in kilometres, miles, and nautical miles — the geodesic measurement GIS and surveying workflows rely on.
📍 Two Coordinates, One Geodesic Distance
What is a Distance Calculator?
It measures how far apart two locations are across the curved surface of the Earth. Give it the coordinates of a start and an end point and it applies the Haversine formula to return the great-circle distance — the true arc over the sphere — in three units at once so you can read it in whichever your workflow uses.
In GIS this is the foundation of proximity analysis, service-area estimates, and route planning. Because it works directly on latitude/longitude, it's the right first step before projecting your data into a local coordinate reference system for detailed measurement.
❓ Frequently Asked Questions
How is the distance calculated?
It uses the Haversine formula to compute the great-circle distance — the shortest path over the surface of a sphere — between two latitude/longitude points, using Earth's mean radius of 6,371 km. The kilometre result is then converted to miles (÷ 1.609344) and nautical miles (÷ 1.852).
Why does GIS use great-circle distance instead of straight-line (Euclidean) distance?
Latitude and longitude are angles on a curved surface, so treating them as flat x/y coordinates distorts distance — badly over long spans and at high latitudes. The haversine great-circle distance measures the true arc across the sphere, which is why it's the default for geodesic measurement in GIS before you project the data.
What datum and Earth radius does it assume?
It models the Earth as a sphere of radius 6,371 km (the mean radius), which is accurate to roughly 0.3% versus the WGS84 ellipsoid used by GPS. For most mapping, logistics, and analysis that's fine; for geodetic-grade work use an ellipsoidal method such as Vincenty's formulae.
How accurate is it and when should I use a projected CRS instead?
Great-circle distance is excellent for point-to-point 'as the crow flies' measurement anywhere on the globe. If you're measuring many features in a small region, reproject to a suitable projected coordinate reference system (e.g. UTM or a national grid) and measure in metres — that keeps local distances and areas consistent.