How to Calculate the Land Area? At site – Geometric Method

In this post, we are going to see how to measure a piece of land at the site using the geometric method.

As you know land measurement is the basic and first thing when comes to any construction. Making minor mistake will lead to heavy loss of our budget. At big sites, there may be someone who will take this hard part.

As a civil engineer, we have the responsibility to understand those basics too.

Let start with the method of calculation. The Actual site may be in any shape so according to the need, we will use any of the below methods.

Method of Calculating Land Area

  • Geometric Method
  • Graph Paper Method
  • Plain Table Survey Method
  • Theodolite Survey Method
  • Using GPS Methods
  • Aerial Photographs

FYI, we are not going to discuss these methods. For the sake of simplicity, we are going to discuss only geometric method now.

Geometric Method

Assuming that you are going to calculate the land area for a small site.

This is the basic method we used at the site. Just understand the shape of the area and start to measure and record as we do for any measurements like length, breadth etc.

We have already published Basic Area Formulas Post for your reference. So using the right shaped formula we can calculate the area of the site quickly.

Geometric Shaped Site Area

Area for Rectangular shaped Site = L X B

Rectangular Shaped Site

Area for Square Shaped Site = A2

Square Shaped Site

Area for Trapezium shaped Site = 0.5 x (A + B) x Height

Trapezium Shaped Site

Here comes the difficult one, Area of Unevenly shaped site

Irregular Shaped Site1

With this shape of uneven area measurements, we have to divide the shape into as many as possible known geometric shapes like triangle, rectangle etc..

Irregular Shaped Site

Here we have divided this into 3 triangles (ABC, ACE, ECD) Using Heron’s formula for area calculation. 

Area = √s(s-a)(s-b)(s-c)  where s = (a+b+c)/2

Area For ABC (A1)


S = (a+b+c)/2   (Where AB=a, BC=b, CA=c)

  = (5+4+5.5)/2 = 7.25

Area = √s(s-a)(s-b)(s-c) = √7.25(7.25-5)(7.25-4)(7.25-5.5)

A1 = 3.58 m2

Area For ACE (A2)


S = (a+b+c)/2   (Where AC=a, CE=b, EA=c)

  = (5.5+8+6)/2 = 9.75

Area = √s(s-a)(s-b)(s-c) = √9.75(9.75-5.5)(9.75-8)(9.75-6)

Area = 16.49 m2

Area For ECD (A3)


S = (a+b+c)/2   (Where EC=a, CD=b, DE=c)

  = (8+5+5)/2 = 9

Area = √s(s-a)(s-b)(s-c) = √9(9-8)(9-5)(9-5)

A3 = 12 m2

Total Area = A1+A2+A3 = 3.58+16.49+12 = 32.07 m2

Total Area = 32.07 m2

Hope you enjoyed the content. Happy Learning 🙂