Map Area Calculator
Click up to 30 points to trace any shape on the map -- a lot, a park, a building footprint -- and get its area in acres, hectares, square kilometers and square miles, plus its perimeter.
Search powered by OpenStreetMap Nominatim, limited to one lookup per second. Didn't find it? Click the map instead.
Click to add each corner of your shape, in order, up to 30 points. Map data © OpenStreetMap contributors.
Click the map to place your first point.
The method, and a worked example
This tool sums, for each edge of your polygon, Δλ × (2 + sinφ1 + sinφ2) (Δλ is the change in longitude in radians between the edge's two endpoints, φ1 and φ2 are their latitudes), then multiplies the total by R²/2 (R = 6,371.0088 km, the same Earth-radius constant used throughout this site) and takes the absolute value.
Worked by hand: a roughly 1 km × 1 km square near the equator (side length ~0.00899°, since 1° of longitude at the equator is about 111.195 km) computes to:
| Square meters | 1,000,000.0 |
| Square kilometers | 1.00 |
| Acres | 247.1 |
| Hectares | 100.00 |
A near-perfect 1.0 sq km, exactly as expected for a 1 km square -- checked against this same hand-derived figure in the site's own test suite, not just displayed here.
Unit conversions used
Once the area is computed in square meters, every displayed unit is an exact conversion: 1 acre = 4,046.8564224 sq m (the international acre, derived from the international foot), 1 hectare = 10,000 sq m exactly, and 1 sq mile = (1,609.344 m)² = 2,589,988.110336 sq m, using the same exact mile constant as the Distance Between Two Points page.
Frequently Asked Questions
How is the area of an irregular, hand-drawn shape actually calculated?
With the Chamberlain-Duquette spherical-excess formula -- the same method behind the Google Maps JavaScript API's geometry.spherical.computeArea and the open-source Turf.js library's area function. It sums, for each edge of your polygon, the change in longitude weighted by the sine of the two endpoint latitudes, which gives an area on the sphere's curved surface rather than treating your points as if they were on a flat plane.
Why does it matter that this accounts for the sphere, not just a flat plane?
For a small shape -- a lot, a park, a neighborhood -- a flat-plane (planar) approximation and a spherical calculation come out nearly identical, within a tiny fraction of a percent. The difference grows as your polygon gets larger or moves toward higher latitudes, where lines of longitude are closer together than they are near the equator; a spherical formula accounts for that automatically, where a naive flat calculation would not.
Do the points need to be in a specific order, like clockwise?
No -- click your points in the order they appear around the shape's edge (either clockwise or counterclockwise both work), and the tool automatically closes the shape back to your first point. Clicking points out of order (crossing the shape's own outline) will still compute a number, but it won't represent the area you intended -- undo and re-click if a shape looks self-intersecting on the map.
What's the difference between this and drawing a circle on the homepage?
The homepage and the Circle on a Map page draw a perfect geodesic circle from a centre and radius -- fast, but only useful if your area actually is roughly circular. This page traces an arbitrary shape point by point, which is the right tool for an irregular lot, a building footprint, or any boundary that isn't close to a circle.
How accurate is this for a real property boundary or legal document?
It isn't survey-grade, and it shouldn't be used as one. Accuracy depends entirely on how precisely you click each corner relative to the underlying map imagery, which itself has its own resolution limits. For anything legal, financial or safety-critical -- a property line, a permit application, a construction plan -- use a licensed surveyor's measurement, not this tool.
Every distance, area and radius on this site is a geometric estimate from the coordinates you provide, not a survey-grade measurement -- and this tool does not calculate driving routes or travel time. See the Terms.