Hello everyone, in this article, I am going to show you how to calculate area of a polygon using QGIS. In some cases, you may want to know how many hectares of an area in a layer. If you have one polygon, this would not be a problem. But what if you have many polygons/areas in the layer? To calculate each area one by one is almost impossible. So, I hope this tutorial will help you solve this problem.
So let’s assume we have a layer with many polygons in it. And then, we are going to calculate the area for each polygons using automated way.
As you can see above, I have a layer with so many polygon in it. If we open the attribute layer, it showing like this
OK, lets do it.
First, we need to make sure the measurement unit for our QGIS project. Go to File >> Properties to change the measurement unit. For example, you can change the ellipsoid for the distance and area calculation. In this example, I use none/planimetric. This means the area calculation will use the planimetric method. And then, change the units for the area measurement. In this case, I use Hectares.
Next, open the “Field Calculator”. Here I want to create a new virtual field to store the area calculation for each polygon. I choose Decimal number (double) on the output field type.
To calculate the area, use the $area expression. You can find this expression under Geometry. See the picture above. Click OK and it will automatically calculate the area for each polygon. Once done, open the attribute table to see the result.
Now I have a new column called Area_calculation which contains total area for each polygon.