How to calculate land square metres, decares and hectares
Land area calculation is based on a closed polygon, but CRS, corners, GPS noise and slope affect interpretation.
Field takeaways
- 1 decare is 1000 square metres and 1 hectare is 10000 square metres.
- Area calculation needs a closed polygon and meaningful boundary vertices.
- Phone GPS is useful for approximate work, not official precision.
- Metric area needs suitable CRS handling.
- MapLab Survey keeps area, perimeter, notes and exports together.
Area comes from geometry
Square metres are computed from the polygon you captured, so the number is only as good as the corners. Two careless corners can move the result by several per cent.
Close the shape
An open polygon reports the wrong area, and most software closes it silently between the last and first point.
Horizontal by convention
Reported area is the horizontal projection. On sloping ground the surface area is larger, which matters for materials but not for land records.
Convert once, at the end
Work in square metres and convert to decares or hectares only when presenting, so rounding does not accumulate through the calculation.
Try these steps on your own phone.
MapLab Survey handles RTK/GNSS point capture, drawing, area and volume calculations and coordinate conversion, then exports to DXF, KML/KMZ, GeoJSON, Shapefile, GeoPackage, NCZ or CSV. Capture, calculation and export work offline. Live NTRIP corrections and online basemaps need a connection.
Frequently asked questions
How is land area calculated?
By calculating the area of a closed boundary polygon.
How many square metres is one decare?
1000 square metres.
Is phone area measurement reliable?
For approximate work, yes. For precision, use controlled survey methods.
Why can deed area differ?
Boundary interpretation, method and CRS can differ.
Technical references
The field guidance in this article is aligned with the technical and official references below.
Related: Field area calculation · Area measurement app · Registry area comparison · MapLab Survey