I am needing to find the largest distance between 2 vertices of a polygon in QGIS.

I am aware I can just use the measuring tool but sometimes I can have over 400 polygons to measure so ideally this would be automated. I assumed since I can automatically measure the area, there would also be a way to measure the diameter.

  • Here is a related post where the largest line should not cross the polygon boundary or inner hole.
    – JGH
    Sep 16 at 14:33

1 Answer 1


There is a tool called Minimum enclosing circles in the processing toolbox.

This algorithm calculates the minimum enclosing circle which covers each feature in an input layer.

See the 'Minimum bounding geometry' algorithm for a minimal enclosing circle calculation which covers the whole layer or grouped subsets of features.

  • That's perfect thanks! I've used that which provided me a radius. And then used the field calculator to multiply that column by 2 which has given me the info I need. Thanks a lot!
    – Gregor
    Sep 16 at 14:51

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