How to Work Out the Land Area of an Odd Shape

Generating the surface area of a plot of land is important for tax assessment, easement determinations, building permits and more. It's all well and good when the land area is done in rectangular or square lots, but when the parcel is a polygon of some sort, it's a bit trickier, and requires some trigonometry.

Things You'll Need

• A scale drawing of the plot of land
• Ruler
• Compass
• Calculator and scratch paper or spreadsheet

Instructions

1. Get a drawing of the plot of land that's to scale, and has all of the angles and lengths marked.

2. Determine the scale of the drawing, so that you know how many millimeters on the drawing translate to how many feet on the land.

3. Subdivide the drawing into right angle triangles with a ruler and a compass. The side of a right angle triangle opposite the 90-degree corner is called the hypotenuse.

4. Measure the length of the hypotenuse and the height from the hypotenuse to the right angle corner for each triangle.

5. Calculate the surface area of each triangle by the formula of length of hypotenuse times the height to the triangle times one half. In Excel, if the length were in cell A1, and the height were in B1, the formula in C1 would be "=A1*C1*0.5".

6. Repeat Step 5 for each right triangle. Sum the areas of all the right triangles.

References

• Calculating the Land Area With Right Triangles
• Breaking Down Polygons Into Right Triangle