A polygon feature layer must be loaded into ArcMap in order to use this
tool. Select the feature layer you wish to process from the drop-down box and choose between the option to add new field(s) or updates existing field(s). You can add/update either AREA, or PERIMETER, or both - this is controlled using the AREA and PERIMETER check mark boxes. If you are adding new fields note that the field names should be 10 characters or shorter, with no spaces or special characters (e.g. %*,';:" etc), and should not start with a number.
You can activate the multiplier by checking the "Convert area units" box or the "Convert perimeter units" box. Note that by default the units are the units of the coordinate system (AREA: m^2 for UTM, ft^2 for SPC, etc; PERIMETER: m for UTM, ft for SPC, etc). If you use a multiplier for the area and perimeter, note that the multiplier for the perimeter will almost always be the square root of the multiplier for the area.