Polygon Centroid Finder — Find the Center Point of Any Polygon
Draw polygons on the map, or upload a GeoJSON file or a zipped Shapefile, and find the center point of each polygon with one click. Every layer can get its own color. Save the center points as a GeoJSON file — fast, in your browser, with no extra program needed. Open in full screen ↗
A centroid is the center point of a shape. For a simple round or square shape, this point is easy to guess. But for a real polygon, like a city block, a farm field, or a country border, the center point is not always where you think. This tool finds that point for you, for one polygon or for many polygons at the same time.
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How the Centroid Is Found
The tool looks at all the points of a polygon and finds the average position. This is not always the exact middle you would draw by eye, but it is the mathematically correct center of mass for the shape. For a strange or long shape, the centroid can even fall a little outside the polygon — this is normal and expected.
Only Polygons Work Here
This tool only accepts closed shapes: Polygon and MultiPolygon. Points and lines do not have a center point in the same way, so they are not allowed as input. If your file has other shapes mixed in, the tool keeps only the polygons and tells you how many other shapes it did not use.
Two Ways to Add Your Polygons
Add the polygons you want to check with one of these methods, or use both together in the same session:
Draw on the map: Click "Draw Polygon", then click the map to add each corner. Finish the shape with a double-click, the Enter key, or the "Finish" button. All shapes you draw go into one "Drawn Polygons" layer.
Upload a file: Click "Upload" or drag a file onto the map — a GeoJSON/.json file, or a zipped Shapefile (.zip with .shp, .dbf and .shx inside). Each file becomes its own layer.
No file ready? Click "Sample Polygons" to add a small test set. Once you have at least one polygon layer, pick it in the "Polygon Layer" list, choose a marker color, and click "Find Centroids".
Layer Colors and Marker Style
Two color settings help you tell layers apart on the map:
Polygon Layer color: each polygon layer gets its own color when you add it. You can change this color any time from the layer row.
Marker Color: sets the color of the centroid points before you click "Find Centroids". Change it again after, from the layer row, if you want a different look.
Every new centroid layer stays on the map on its own, next to the polygons it came from, so you can still see both at the same time.
Working with Your Layers
Each polygon layer and each centroid layer you make shows up as one row in the Layers list. From that row, you can turn the layer on or off, change its color, zoom the map to it, save it as GeoJSON, or delete it. None of these actions change any other layer.
Saving Your Centroid Points
Two ways to save your work are always ready in the sidebar:
Save one layer: click the download icon next to any layer row to save only that layer as a GeoJSON file.
Download All Layers: puts every layer on the map — polygons and centroid points together — into one GeoJSON file, with each feature marked with its layer name.
GeoJSON opens without problems in Leaflet, Mapbox GL JS, QGIS and ArcGIS, and it even shows as a live map on GitHub.
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Step by Step
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Step 1
Open the tool
The map opens on a world view with no layers yet. The toolbar at the top has Draw Polygon, Upload, Sample Polygons and a basemap switch. The sidebar on the right has the centroid tool, the layer list, and the export button.
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Step 2
Draw a polygon, or use a sample
Click "Draw Polygon" and click the map for each corner. Finish with a double-click, Enter, or the Finish button. Or click "Sample Polygons" to try the tool right away with three test shapes.
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Step 3
Or upload your own file
Click "Upload" or drag a file onto the map — a GeoJSON file or a zipped Shapefile. The tool keeps only Polygon and MultiPolygon shapes and tells you if it had to leave some shapes out.
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Step 4
Pick the polygon layer
Open the "Polygon Layer" list in the sidebar and pick the layer you want to check. Only polygon layers show up here — centroid layers are not shown, since they are already points.
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Step 5
Choose a marker color
Click the color box next to "Marker Color" and pick a color for the new centroid points.
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Step 6
Click Find Centroids
The tool works out the center point of every polygon in the layer and adds a new point layer with those centroids. The map zooms to fit the new points.
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Step 7
Check and manage your layers
In the Layers list, turn any layer on or off, change its color, zoom to it, or delete it. Centroid layers are marked differently from polygon layers, so you always know which is which.
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Step 8
Try it again with another layer
Pick a different polygon layer, or add more polygons, then click "Find Centroids" again. Each run makes a new, separate centroid layer.
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Step 9
Save your results
Click the download icon on a layer row to save just that layer, or click "Download All Layers" to save every layer — polygons and centroids — in one GeoJSON file.
Real-World Use Cases
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Election and District Maps
Election offices and city planners use the centroid of a district polygon to place the district number on a map, and to check how compact or spread out a voting district really is.
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Cell Towers and Network Planning
Telecom engineers find the centroid of a coverage polygon to check antenna placement, or to pick one new tower site that best serves several overlapping coverage areas at once.
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Property and Land Records
County land offices and real estate platforms use the centroid of a parcel to place the address pin or price label at the true middle of the property, not at a random corner.
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Farm Field Management
Precision farming software finds the centroid of each field boundary to set the starting point for GPS-guided tractors, drones, and irrigation pivots.
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Retail and Delivery Zones
Retail chains and delivery companies turn each store's trade area or delivery zone polygon into one point, then use that point to compare drive times or plan new depot locations.
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Disaster Response and Public Health
Emergency planners find the centroid of a flood zone or a census tract to help decide where to place a relief center or mobile clinic that stays closest to the average resident inside it.
