What is a Voronoi map?
A Voronoi map divides real geography into cells around a set of places. Every location inside a cell is closer to that cell's place than to any other, so each cell shows the area a store, school or station would serve if people simply went to the nearest one. For an abstract diagram without a map, use the Voronoi diagram generator.
- Retail: Defining catchment areas for stores (which store is closest to me?).
- Schools: Planning school districts based on proximity.
- Biology: Understanding cell growth patterns.
How to make a Voronoi diagram on a map
- Search for a city, then click the map to place your sites — stores, schools, clinics, stations or sample points.
- Or open Import coordinates and paste latitude/longitude pairs, or upload a CSV or GeoJSON file.
- Choose where the cells stop: the current map view, a box around your sites, or an uploaded city or district boundary.
- Optionally set a maximum service radius so no cell reaches further than a given distance.
- Pick a palette and labels, read each cell's area in the site list, and copy a link to share the diagram.
Voronoi diagrams vs. Thiessen polygons
They are the same partition under different names. Mathematicians call it a Voronoi diagram (after Georgy Voronoy) or a Dirichlet tessellation. In geography and hydrology it is known as Thiessen polygons, after the meteorologist Alfred H. Thiessen, who used it to weight rain-gauge readings by the area each gauge represents.
How accurate are the cells and areas?
Cells are computed in the Web Mercator plane, the same projection the map is drawn in, so the borders you see match the areas reported for each cell. At city and regional scale this is effectively identical to true nearest-distance on the ground. Across whole countries or continents Mercator stretches distances toward the poles, so treat very large diagrams as a visual guide rather than a measurement.
Each cell's area is measured on the Earth's surface and reported in square kilometers. Remember that a Voronoi cell uses straight-line distance. Where rivers, highways or terrain shape how people actually travel, a drive-time or walk-time map (isochrone) is a better model of a real catchment.
Frequently asked questions
Can I import my own locations?
Yes. Paste latitude/longitude pairs or upload a CSV or GeoJSON file. GeoJSON points become sites and GeoJSON polygons become a clip boundary.
Is my data uploaded to a server?
No. The diagram is computed in your browser. Only place searches are sent to the map provider's geocoding service.
Why do the outer cells look so large?
Cells on the edge of your point set are open on one side, so their size is set by the extent you choose. Clip to a real boundary or add a maximum service radius to get meaningful areas for them.
How do I share a Voronoi diagram?
Use Copy link. The link stores your sites and the map view, so a colleague who opens it sees the same diagram and can keep editing it.
More Voronoi tools
- Spherical Voronoi on a globe — correct cells at country and world scale.
- Weighted Voronoi — let larger stores or hospitals claim more area.
- Voronoi distance metrics — Manhattan (street-grid) distance instead of straight lines.
- Voronoi diagram generator — the same cells on a blank canvas, with relaxation and Delaunay overlay.
- All Voronoi tools — patterns, mosaics, Delaunay, relaxation and more.