Free tool
Calculate the area of a plot of land.
Three ways to find the area of a plot: from the coordinates of its boundary markers (property plan, topographic plan), by drawing its outline on the map, or from lengths measured on site. Everything is calculated in your browser: your coordinates are not sent to anyone (only the map background is loaded from OpenStreetMap).
Enter the boundary markers in the order they follow each other around the plot (either direction), or paste the list from your plan.
Paste a list or import a file (CSV, TXT)
One marker per line: “name ; X ; Y” or “X ; Y”. Separator: semicolon, tab, comma or spaces. For GPS: “name ; latitude ; longitude”. A header line is ignored. The list replaces the markers already entered.
Click or tap the map to place the corners in order around the plot. Drag a corner to move it; click it to delete it; click a side to insert a corner. With the keyboard: move the map with the arrow keys, then “Add the map centre”.
Estimate: accuracy depends on your drawing and on the base map. It does not replace a survey.
Corners drawn
For those who measured with a tape or a laser meter: split the plot into triangles, or measure its 4 sides and one diagonal. Horizontal lengths in metres.
For each triangle, enter its three sides. Triangles must not overlap.
Name the corners A, B, C, D going round the plot. Measure the 4 sides and diagonal AC, which must run inside the plot. The second diagonal BD, optional, is used as a check.
To compare with the area written in a deed, a land title or a listing.
Convert an area (m², ares, hectares)
Your last entry is kept in this browser only; nothing is sent.
Method
How the area is calculated.
From boundary markers, the tool applies Gauss's formula (also called the “shoelace” formula) to the plane X and Y coordinates: it is the exact area of a polygon whose corners are known. With Lambert coordinates, the result is the projected area, the one shown on property and cadastral plans drawn in that system.
From GPS coordinates or a drawing, the corners are first projected to Morocco Lambert (zone chosen from the latitude) with the official parameters of the EPSG registry, then the same calculation is applied.
From lengths, each triangle is calculated with Heron's formula (from its three sides); a quadrilateral is split into two triangles by a diagonal. A second diagonal makes it possible to check that the measurements are consistent.
- Automatic checks: at least 3 markers, duplicate markers, crossing sides (wrong marker order), coordinates outside Morocco or X/Y columns swapped.
- For each side: length and bearing in gon and degrees; for each corner: interior angle.
- Exports: list of points in Lambert and GPS (CSV), outline as KML and GeoJSON, printing.
An exact calculation on wrong coordinates gives a wrong area: the quality of the result depends entirely on the data entered.
Measurement and deed
When the calculated area does not match the deed.
The area stated in an old deed, a melkia or a listing may differ from the measured area. For titled land, the reference is the property plan attached to the title; for untitled land, only a recent measurement is informative. See the guide on cadastral and property plans.
Minimum plot sizes set by planning documents are assessed on the actual area of the land. Before buying, building or dividing, have the land measured: see planning documents and dividing an inheritance.
For titled land or land under registration, the ANCFCC also offers an online “area calculation” (calcul de contenance) document: see ANCFCC online services.
Frequently asked questions
Land area: common questions.
Where can I find the coordinates of my plot's boundary markers?
On the property plan attached to the land title or on the plan of a registration file: markers are usually listed there with their Lambert X and Y coordinates. A recent topographic plan tied to the official system shows them too. A freehand sketch or a plan attached to a melkia usually does not.
How many m² in an are and in a hectare?
One are is 100 m², one hectare is 100 ares, i.e. 10,000 m². Titles and property plans often express the area as “1 ha 23 a 45 ca”: 1 hectare, 23 ares and 45 centiares (1 centiare = 1 m²), i.e. 12,345 m². The tool gives this form with every result.
Can I measure my plot by walking around it with my phone?
A phone's GPS is often several metres out, and the error varies from one point to the next. For a small plot, the error on the area can be large: the tool shows it in the “sensitivity” line. It is useful for an order of magnitude, not for a sale or a division.
Why does drawing on the map only give an estimate?
Accuracy depends on your drawing (one pixel covers several decimetres, or even several metres, depending on the zoom) and on the OpenStreetMap base map, whose feature positions are not guaranteed. The calculation itself is exact; it is the corners that are approximate.
Why does the order of the markers matter?
The formula assumes the markers follow each other along the outline. If two markers are swapped, the outline crosses itself and the area becomes meaningless: the tool detects and reports this. The direction (clockwise or anticlockwise) does not matter.
Is my data sent anywhere?
No. All calculations are made in your browser. Only the base map images are loaded from OpenStreetMap. Your last entry is kept in this browser so you can find it again; the “Clear my data” button deletes it.
References
Technical sources.
Parameters and formats checked on 29 October 2026.
EPSG:26191 — Merchich / Nord Maroc
Parameters of the Lambert conformal conic projection for zone I, used for the calculation.
spatialreference.org ↗EPSG registryEPSG:1136 — Merchich to WGS 84 (1)
Transformation between the Moroccan system and GPS, used to place the plot on the map and for exports.
epsg.io ↗IETFRFC 7946 — the GeoJSON format
Standard followed for the GeoJSON export (WGS 84 coordinates, outer ring anticlockwise).
www.rfc-editor.org ↗OpenStreetMapCopyright and licence
Terms of use of the OpenStreetMap base map.
www.openstreetmap.org ↗Need an exact measurement?
A survey you can rely on.
To buy, sell, divide or register land, we measure your plot with GNSS and a total station, tied to the official geodetic network.
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