Calculate the percentage of area for polygons

Summary

Instructions provided describe how to calculate the percentage of the area of a polygon layer against a larger polygon.

Procedure

Note:
The content in this article pertains to ArcGIS versions 9.x and 10 only. Later versions of ArcGIS may contain different functionality, as well as different names and locations for menus, commands and geoprocessing tools.

Select the appropriate procedure based on the ArcGIS license level used.

These examples use 'parcels' polygons to calculate their areas as a percentage of a larger 'county' polygon.

Procedure for ArcView

1. Launch the Intersect tool from Toolboxes > System Toolboxes > Analysis Tools > Overlay toolset.
2. Select the 'parcels' layer and the 'county' layer as the Input Features.
3. Specify a name and location for the Output Feature Class.
4. Under JoinAttributes, select ALL, and click OK.
5. Add a new Double field, for example, 'InterArea', to the result of the Intersect.
6. Right-click 'InterArea' and select Calculate Geometry.
7. Select Area as the Property.
8. Use the coordinate system of the data frame.
9. Select the desired units, and click OK.
10. Add another new Double field, Percentage, and run the Field Calculator, where 'OrigArea' is the original Area field from the 'county' layer:

[InterArea] / [OrigArea] * 100.

Procedure for ArcInfo

1. Launch the Identity tool from Toolboxes > System Toolboxes > Analysis Tools > Overlay toolset.
2. Under Input Features, select the 'parcels' layer.
3. Under Identity Features, select the 'county' layer.
4. Specify the name and location of the Output Feature Class.
5. Under JoinAttributes, select ALL.
6. Click OK to run the tool.
7. Add a new Double field, for example, 'InterArea', to the result of the Identity operation.
8. Right-click 'InterArea' and select Calculate Geometry.
9. Select Area as the Property.
10. Use the coordinate system of the data frame.
11. Select the desired units, and click OK.
12. Add another new Double field, 'Percentage', and run the Field Calculator where 'OrigArea' is the original Area field from the 'county' layer:

[InterArea] / [OrigArea] * 100