Most real plots — especially older or resurveyed ones — have four unequal sides because the boundary follows a road curve, a neighbouring wall, or a historical land division. Multiplying "length x breadth" on such a plot gives a wrong area, sometimes very wrong. Splitting the plot into two triangles along one diagonal and measuring each triangle's true area gives the correct total.

Deeds are sometimes based on old or approximate measurements. Recomputing from the actual boundary lengths (and comparing to the deed and RERA-registered area) is a quick way to check that you are paying for the land you are actually getting.

A link (1 link = 0.66 ft = 0.201168 m) is a traditional Indian survey unit still used in some old patta and FMB (Field Measurement Book) records. If your document lists lengths in links or chains, select Links so the area comes out correct without manual conversion.

The calculator checks that each of the two triangles formed by the diagonal obeys the triangle inequality (no side longer than the other two combined). If a triangle isn't possible with your numbers, it flags this instead of showing a wrong area — re-check the side or diagonal you measured.