JoseFitani
🗺️ Area & Perimeter

Area Calculator

Calculate the area of any land polygon by entering its vertices. Results in km², m², hectares, acres and mi².

This page explains how the area calculator works, the data and formulas behind it, and how to interpret the result. The spherical excess formula gives the exact area of a polygon on a sphere. It works for polygons of any size, from small plots to entire countries, and is accurate to within ~0.1% of the more complex ellipsoidal formula. The tool is one of 329 free, open tools on JoseFitani for maps and geography. It runs in your browser with no sign-up needed. Use the search field or click the map to drop a pin - the tool uses the spherical excess formula for area on a sphere, plus great-circle distances for perimeter and returns the result in seconds. Below you'll find a step-by-step guide, real use cases, the methodology, FAQs, and data sources.

Click on the map to add vertices. The polygon will be drawn and the area calculated in real time.

Loading map…
0 vertices

How to use this tool

1
Enter your input

Type your query, paste coordinates, or click on the map. The tool uses the spherical excess formula for area on a sphere, plus great-circle distances for perimeter to process your input locally in the browser.

2
View the result

The result appears instantly with the map showing your location. You can adjust by clicking elsewhere or searching a new place.

3
Copy or share

Click Copy to save to clipboard, or Share to send a direct link with the exact inputs.

What people use this tool for

Farm and land valuation

Buyers compare asking prices against the true extent of a parcel, not the rounded figure on a listing. Tracing the boundary on this tool yields the area in hectares and acres side by side. That number anchors negotiation and loan paperwork.

Example: A buyer in Punjab traces a 2.4-hectare wheat plot and finds the listed '6 acres' is really 5.9, which reshapes the per-acre price discussion.
Construction site measurement

Contractors estimate earthwork, paving, and landscaping costs from the site footprint before breaking ground. A quick polygon over the plot gives square metres and acres for the bill of quantities. Rough tape measures and guesswork introduce errors that compound across a large site.

Example: A contractor in Surat measures an irregular warehouse plot to price the concrete slab, and the polygon catches a corner the site plan had smoothed over.
Reservoir and lake monitoring

Environmental teams track how water bodies shrink or grow between seasons from satellite imagery. Outlining the shoreline each visit produces a comparable area figure in square kilometres. Repeating the measurement on the same boundary style shows the trend without field visits.

Example: A researcher traces a reservoir in Rajasthan in October and again in May, documenting a seasonal contraction that supports the drought assessment.
Park and green-space planning

Urban planners balance built-up area against mandated green cover when reviewing proposals. Measuring each green patch in hectares shows whether the development meets the open-space ratio. The spherical-excess method keeps large districts accurate where flat maps distort.

Example: A planning team in Bengaluru measures three proposed parks to confirm they total the 15 percent green cover the master plan requires.

How it's calculated

Area is computed on the curved surface of the Earth using a spherical excess formula. Each vertex is a lat/lng pair.

The calculation runs in your browser - no data is sent to our servers. Map tiles come from OpenStreetMap (ODbL license), geocoding uses Nominatim (1 request/second limit), and elevation uses the Open-Elevation API backed by SRTM data. All are free, open services.

All calculations use the WGS84 datum (EPSG:4326), the same as GPS. For other datums (NAD27, NAD83, ETRS89), a separate conversion is needed. The difference is typically under 1 metre - negligible for most uses but important for survey-grade work.

The formulas match those in professional GIS software (QGIS, ArcGIS, Global Mapper), just in a browser-friendly form. For sub-metre accuracy, use professional software with ellipsoidal calculations. Results are shown in multiple units: km and miles for distance, km²/m²/hectares/acres for area, metres and feet for elevation. Conversion factors are exact (1 mile = 1.609344 km), so the only error source is input precision.

Related tools and resources

For more tools in this category, explore the related tools listed below. Each tool includes full documentation, examples and FAQs. Explore related tools in our Area category for complementary functionality. See the Tools index for all 329 tools, or read our blog for in-depth articles on geography and maps.

Frequently asked questions

Does this work for small plots?

Yes - but for sub-hectare plots, projection-based tools are more accurate.

How does this tool calculate area?

It applies the spherical excess formula to the polygon you trace, which treats the earth as a sphere instead of a flat plane. Flat-map formulas grow increasingly wrong as parcels get larger or sit far from the map projection's sweet spot. The spherical method stays accurate from a garden plot up to a whole country.

How accurate is the result?

The math itself is exact for the vertices you place; the real limit is how precisely you position each corner. On a large farm, a vertex a few metres off changes the total by a fraction of a percent. For legal surveys you still need a licensed surveyor, but for estimates and comparisons this is more than sufficient.

Does the order of the vertices matter?

Yes, list them in sequence around the boundary, either clockwise or counter-clockwise, without jumping across the shape. If two edges cross, the polygon becomes self-intersecting and the computed area loses its meaning. Tracing the fence line in the order you would walk it is the safest approach.

Can it measure areas with holes, like a courtyard?

The basic polygon method measures the whole outline including any hole inside it. For a courtyard building, measure the outer footprint and the inner courtyard separately, then subtract. That two-step subtraction gives the true built-up area.

Why do I get a different number than a rectangle estimate?

A rectangle estimate ignores every deviation of the real boundary from four straight sides. Irregular parcels, curved river frontages, and diagonal fences all change the true area. The polygon method follows the actual shape, so it usually comes out smaller than a generous length-times-width guess.

Which units are shown and why so many?

Results appear in square kilometres, square metres, hectares, acres, and square miles because different trades speak different units. A farmer thinks in acres, a city planner in hectares, and an engineer in square metres. Showing all five saves you a separate conversion step.

Does it work near the poles or across the antimeridian?

The spherical excess formula handles high latitudes correctly where flat projections fail badly. Polygons crossing the 180-degree meridian need care: keep longitudes continuous, for example using 179 and 181 rather than 179 and -179, so the polygon does not wrap the wrong way around the globe.

Does the measurement need an internet connection?

Only to load the page. The area computation runs entirely in your browser from the vertices you enter. You can trace a polygon in the field on a loaded page with no signal and still get the result.

Data sources & methodology