Irregular plot area calculator (4 sides with a diagonal, rectangle, triangle)
Four side lengths alone do not fix the shape of a quadrilateral; it can flex, so the common "average length × average width" formula over-estimates most real plots. Measuring one diagonal splits the plot into two triangles whose areas are exact.
- Area in gaj (sq yd)
- 264.20
- Area in sq m
- 220.90 sq m
- Method used
- Exact: two triangles via Heron's formula using diagonal AC
- Average-method estimate (for comparison)
- 2,379 sq ft
Copy link to this calculation · JSON API · Estimates only; verify rates with the source below.
How it is calculated
With sides a, b, c, d and diagonal p splitting the plot into triangles (a, b, p) and (c, d, p), each triangle's area is √(s(s−x)(s−y)(s−z)) where s is half its perimeter (Heron's formula); the plot area is their sum. For a rectangle enter equal opposite sides and the diagonal √(a² + b²). Without a diagonal the tool falls back to the average method and labels it approximate.
Worked example
Sides 40, 62, 38, 60 ft and diagonal 72 ft: triangle 1 (40, 62, 72) = 1,238 sq ft, triangle 2 (38, 60, 72) = 1,140 sq ft, total 2,378 sq ft = 264 gaj. The average method happens to give 39 × 61 = 2,379 sq ft here because this plot is nearly rectangular; on a skewed plot it can be off by 10% or more.
Frequently asked questions
How do I calculate the area of a plot with 4 different sides?
Measure one diagonal as well. Split the plot into two triangles along it and add their Heron's-formula areas. Four sides alone cannot give an exact area.
What is the formula for irregular land area?
For a quadrilateral: area = Heron(a, b, p) + Heron(c, d, p) where p is a diagonal. For more than four corners, measure diagonals from one corner to split into triangles, or use coordinates (shoelace formula).
Why does my patwari's area differ from the average method?
Revenue records use measured triangles or coordinates. The average-of-sides shortcut assumes right angles, so it overstates area on plots with slanted sides.
Sources and what to verify: Heron's formula; survey practice for quadrilateral plots.
Estimates for planning only; not financial, legal or tax advice. Figures reflect common practice and published rates as of November 2026. Found an outdated rate? Email hello@zeorent.com.