Please cite SAGA whenever you use it for your publications:

Add general and geometric properties of polygons to its attributes.

Name	Type	Identifier	Description	Constraints
Input
Polygons	shapes, input	POLYGONS
Output
Polygons with Property Attributes	shapes, output, optional	OUTPUT	If not set property attributes will be added to the original layer.
Options
Copy Attributes	table fields	FIELDS	Select one or more attributes to be copied to the target layer.
Number of Parts	boolean	BPARTS		Default: 0
Number of Vertices	boolean	BPOINTS		Default: 0
Extent	boolean	BEXTENT		Default: 0
Centroid	boolean	BCENTER		Default: 0
Perimeter	boolean	BLENGTH		Default: 1
Area	boolean	BAREA		Default: 1
Scaling	floating point number	SCALING	Scaling factor for perimeter and area (squared). meter to feet = 1 / 0.3048 = 3.2808	Minimum: 0.000000 Default: 1