I need to do calculations of surfaces of polygons in vector layers. The clip tool does just what I want - I can clip the polygons of the input layer to the clipping layer. When I project the new layer I can see that the polygons are indeed clipped along the polygon border of the clipping layer. So that worked.

However, when I check the attribute table, the surface of the clipped new polygon is still equal to the original polygon surface. In the manual it says: "The attributes of the features are not modified, although properties such as area or length of the features will be modified by the clipping operation. If such properties are stored as attributes, those attributes will have to be manually updated."

Now, HOW do I manually update these attributes? All instructions I have found so far stop after the clipping and none goes into the updating of the attribute table...

  • 2
    What software are you using?
    – Bjorn
    Commented Nov 16, 2020 at 14:19
  • sorry, QGIS....
    – user172780
    Commented Nov 17, 2020 at 5:48

1 Answer 1


Use the field calculator, inserting the expression $area or area($geometry).

See here for details: https://gis.stackexchange.com/a/23356/88814

A tutorial with more information here: https://www.northrivergeographic.com/qgis-calculating-an-area

  • thanks - I obviously kept searching with the wrong key words, so thanks for posting the link to the solution!
    – user172780
    Commented Nov 18, 2020 at 7:54

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.