6.6.4. Raster calculator
The raster calculator is used for more advanced raster calculations, including raster math and building conditional and trigonometric expressions. It can be found using the search window or in the Spatial Analyst > Map Algebra toolset. For example, the formula “aster30_frib_ch.tif" * 3.28084” would convert the elevation data in the DEM from meters into feet by creating a new raster image.
For more information search “raster calculator” in the help menu (http://resources.arcgis.com/en/help/main/10.1/).