I want to calculate what percentage of each grid square is covered by part of a polygon shapefile in QGIS. So far I can get a column of whether a grid square touches the polygon or not (0 or 1), but I want to know the percent overlapped in each cell. Grid is in red, polygon is in yellow.

Perhaps join features?

1 Answer 1


In Processing Toolbox, search for Overlap analysis and you will find the tool that will do what you want:

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From the tool help:

This algorithm calculates the area and percentage cover by which features from an input layer are overlapped by features from a selection of overlay layers. New attributes are added to the output layer reporting the total area of overlap and percentage of the input feature overlapped by each of the selected overlay layers.

  • Many thanks. It produces 2 new output columns in the attribute table. I'm assuming the output column layername_pc means percent coverage out of 100 (e.g. 1.2 = 1.2%, 0.43 = 0.43%), and layername_area means the area of each feature covered. However, what is the unit of layername_area?
    – MapDeath
    Jul 14, 2020 at 16:24
  • @MapDeath The unit of layer_name area will be same as the layer projection (CRS) unit. For example, if the layer is using UTM projection, it will be in meter square, and if the layer is using WGS 84, it will be in decimal degree. Look at the layer's CRS from the information tab under layer properties to confirm the unit of the CRS.
    – ahmadhanb
    Jul 14, 2020 at 23:31

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