Instructions provided describe how to convert values in the area field into acres.
Note: This article pertains to ArcGIS versions 8.x and 9.x. Later versions of ArcGIS may contain different functionality, as well as different names and locations for menus, commands and geoprocessing tools.
If the data is stored in a geographic coordinate system, which uses units in decimal degrees, the data must be projected to a projected coordinate system which uses a linear unit of measure like meters. Because decimal degrees are angles, an area calculation based on decimal degrees cannot be converted to a usable unit of measurement.
Refer to the article: How to select a suitable map projection or coordinate system in the Related Information section for more information about selecting an appropriate projected coordinate system for data.
Note: Area for polygons in a geodatabase feature class is calculated automatically by the software
Note: Define the new field as DOUBLE. The precision is the length of the field, and the scale represents the number of decimal places. A precision of 18, and scale of 3, for units of feet or meters in a projected coordinate system should accommodate the values to be stored in this field.