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Geographic Center Finder

The centre of a shape is not a matter of opinion once you fix the method. This tool computes the area-weighted centroid and shows exactly where it lands.

How to use it

  1. Pick a country, or a US state, from the list.
  2. The centroid is computed and pinned on the map with the outline around it.
  3. Copy the coordinates in decimal degrees or DMS. The line under the result says whether the centre falls on land or at sea.

How it works

For a country the tool takes its Natural Earth 1:110m outline, converts each vertex to a 3D unit vector, computes the area-weighted mean of the polygon (each part of a multipart country weighted by its spherical area) and projects that mean back to the surface. This is the centre of mass of the surface, the usual definition of a geographic centre; for countries with far-flung islands (France, the United States) it can land in the sea.

For a US state the centre is the land-area-weighted mean of the state's county centres from the Census Gazetteer that powers this site, which matches the Census Bureau's own centres of population method applied to land area. Official "geographic centres" published by states were often fixed by other methods, so they can differ by tens of miles.

Questions

Where is the geographic centre of the United States?
For the 50 states, the Census Bureau puts it near Belle Fourche, South Dakota. For the 48 contiguous states it is near Lebanon, Kansas. This tool computes the country from its outline, including Alaska and Hawaii, so it lands near the South Dakota figure.
Why does the centre of a country fall outside it?
A centroid is a mean, and the mean of a crescent or a chain of islands lies in the hollow. Indonesia, the Philippines and Chile are examples.
Is this the same as the official centre?
Often close but not identical. Official figures depend on the outline used (with or without islands and water), the map projection, and sometimes local tradition. This tool states its method so the answer is reproducible.

All map tools, free and without an account. Location data is processed in your browser and by the open geocoding services named on the sources page; nothing is stored by this site.