GeoJSON Convex Hull Calculator
LocalConvex hull calculator for GeoJSON points: minimum enclosing polygon with vertex count and geodesic area — free in your browser, nothing uploaded.
Sample data loaded — click "Compute convex hull" to try it.
Tip: press Ctrl/⌘+Enter to run
The hull output carries geometry only (empty properties) — input attributes are not preserved; keep your source layer. The result is previewed on the map below; tick "Show original" to compare with the input points.
What is it? GeoJSON Convex Hull computes the minimum enclosing polygon (convex hull) around GeoJSON points and reports vertex count and geodesic area. One paste, one click — free with no sign-in, no desktop GIS or command line needed, and nothing uploaded.
TL;DR: Get the convex hull (minimum enclosing polygon) of GeoJSON points — with vertex count and geodesic area, computed locally in your browser. Free, no sign-in.
How to use
- Paste GeoJSON points, load a .geojson/.json file via "or load a file", or keep the sample that is already filled in.
- Click "Compute convex hull" (or press Ctrl/⌘+Enter).
- Check the vertex count / geodesic area summary, compare against the input on the map preview ("Show original"), then copy or download hull.geojson.
FAQ
Multiple groups?
A single hull over all points is produced.
Why did my points fail?
The hull needs at least 3 distinct points that are not all on one line. The error tells you which case applies: fewer than 3 distinct points (duplicates don't count), or all points collinear.
Is it local?
Yes.
Is it free? Do I need an account?
Yes — computing a convex hull uses the free daily allowance and needs no sign-in. Batch runs and larger quotas are the paid Pro tier.
What is a convex hull?
The smallest convex polygon that contains every point of the set — like stretching a rubber band around pins on a board. Synonyms you'll see in GIS: minimum enclosing polygon, minimum bounding polygon. Use it to outline GPS tracks, sample plots or facility clusters as one clean boundary.
My points are a plain coordinate list or CSV, not GeoJSON — can I still use this?
Yes. Wrap each coordinate as a Point feature in a FeatureCollection — {"type":"Feature","geometry":{"type":"Point","coordinates":[lon,lat]}} with longitude first — then paste it. Or run CSV to GeoJSON first and paste the result here.
Is the math the same as turf.js or ArcGIS convex hull?
The geometry is turf.convex (turf.js, MIT) running in your browser — the same hull a desktop GIS computes for the same WGS84 input, without installing anything. The area summary is spherical geodesic (same formula as turf.area, sphere radius 6,371,008.8 m), within ~0.5% of the exact ellipsoid value at most.
Convex or concave hull?
Convex only here — the minimum enclosing polygon fills in bays and notches. A concave hull (alpha shape) hugs the outline of a point cloud with dents; this tool does not produce one — use a desktop GIS or map editor for that.
Examples
- Paste a point set → get the convex hull polygon with a vertex/area summary
- Paste 50 GPS track points → get the hull boundary with vertex count and area in km², verified against the input on the map before downloading.
Supported formats
Limitations
- Needs at least 3 distinct points not all on one line — errors name the real cause (too few distinct points vs. all collinear).
- Convex hull only (no concave hull here).
- Output is the hull polygon itself (empty properties); input attributes are not kept.
- The area summary uses spherical geodesic math (same formula as turf.area, sphere radius 6,371,008.8 m).
- The map preview renders geometry locally; CARTO basemap tiles are fetched over the network.
Privacy
Privacy first: this tool runs entirely in your browser — your input and files never leave your device, and everything is cleared when you close the page.