How to obtain buffered polygon area size

Question

I have QGIS 3.16. I have several polygons in one layer, added via field calculator the area_ha field (geometry area$/10000) and then buffered all the polygons (buffer, 300 m). Now I need to know the area size (in ha) of the buffered area. Even when I create a new area_ha field (geometry area$/10000) in the buffered layer, I still get the area size of the un-buffered polygon. How do I obtain the area size of the buffered polygons? I don t use Python or any coding and am not familiar with it.

Answer 1

You need to calculate the new area in the buffer layer and then use the "Join attributes by location"(vector->data management tools -> Join attributes by location) to bring the calculated values (buffered areas) into the original table