GeoJSON Area Calculator
LocalCalculate GeoJSON area, length, vertex count and bounding box in your browser — free, no sign-in, nothing uploaded.
Sample data loaded — click "Measure & stats" to try it.
Method: area/length use spherical geodesic math (turf.js, sphere radius 6,371,008.8 m) — up to ~0.5% different from exact WGS84 ellipsoid values (more at high latitudes / long distances); coordinates are read as WGS84 lon/lat. Totals span all features; polygon length is the perimeter. The input is shown on the map preview below so you can verify what you measured.
What is it? GeoJSON Area Calculator computes total area, length, vertex count and bounding box for GeoJSON features with spherical geodesic math (turf.js, sphere radius 6,371,008.8 m), and shows the input on a map preview so you can verify what you measured — runs locally in your browser, nothing uploaded.
TL;DR: Calculate GeoJSON area, length, vertices and bounding box — free in your browser, no sign-in, nothing uploaded.
How to use
- Paste your GeoJSON into the input box, or click "or load a file" to pick a .geojson/.json file.
- Click "Measure & stats" or press Ctrl/Cmd+Enter.
- Read the totals (features/vertices/area/length/bbox) and check the input on the map preview below, then copy or download the results as measure.txt.
FAQ
How is area computed?
Spherical geodesic area (turf.js, sphere radius 6,371,008.8 m). This differs from exact WGS84 ellipsoid values by up to ~0.5% (more at high latitudes / long distances) — the same caliber as most web GIS measure tools.
Is it local?
Yes.
Does it report per-feature measurements?
No — it reports overall totals for the whole input (features, vertices, area, length, bounding box); there is no per-feature detail table.
What units are the results in?
Area is shown in square metres and square kilometres, length in kilometres. Polygon length is the perimeter, and points and lines contribute no area.
Is it free? Do I need an account?
Yes — measuring a GeoJSON file uses a free daily allowance with no sign-in. Batch runs and larger quotas are the paid Pro tier.
How do I calculate the area of a GeoJSON polygon?
Paste your FeatureCollection or polygon, or load a .geojson/.json file, then click "Measure & stats" — the total area comes back in m² and km², and the map preview shows the geometry so you can sanity-check it. MultiPolygon areas sum all member rings.
Is this the same math as turf.js area and length?
Yes — the geometry is turf.js (MIT) spherical geodesic math (R = 6,371,008.8 m) running in your browser, so turf.area / turf.length give the same numbers. This page exposes them without writing code, plus vertex counts and bounding box.
Why do the numbers look wrong?
The input must be WGS84 longitude/latitude. GeoJSON in a projected coordinate system will measure at silently wrong values — reproject to WGS84 first (e.g. with GeoJSON Reproject), then measure here.
Examples
- Paste GeoJSON (or load a file) → get area/length/bounding box + a map view of what you measured
- Load a parcel GeoJSON → read the total area in m²/km² plus perimeter, and check the parcel on the map preview.
- Drop a GPS track GeoJSON → get total length in km with feature and vertex counts.
Supported formats
Limitations
- Spherical geodesic area/length (turf.js, sphere radius 6,371,008.8 m) on WGS84 lon/lat coordinates — up to ~0.5% different from exact ellipsoid values.
- Totals only — no per-feature table export.
- Points and lines contribute no area; polygon length is the perimeter.
- The input map preview renders geometry locally; CARTO basemap tiles are fetched over the network.
- Runs locally in your browser; nothing is uploaded.
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.