Geographic Information Systems
Washington University in St. Louis
Converting (reprojecting) between coordinate systems
Tip: The method described below takes data with known spatial reference and converts it to another coordinate system. To define a coordinate system for data that does not yet have spatial reference, see Specifying a coordinate system.
The Project tool in the ArcToolbox is used if data in one coordinate system needs to be converted, or reprojected, into another system. For example, you may have data that was taken in latitude/longitude under the WGS 1984 geographic coordinate system, but you would like to convert it into an x,y coordinate projection system, such as a UTM projection.
The Project tool can be accessed by clicking the ArcToolbox button 
to open the toolbox panel. Then, go to Data Management Tools > Projections and
Transformations > Feature > Project if you are projecting a shapefile or feature classes. You will be able to select the input file, an output file, and the new coordinate system desired.
Note: To reproject raster data, you will need to use the Project Raster tool under Data Management Tools > Projections and Transformations > Raster instead.
