I am trying to calculate the area of polygons in a shapefile on QGIS 2.2. My project is in an equal area conic projection with OTF projection activated. When I added a new field called 'AREA' and used the $area function in the field calculator, I got impossibly small numbers. I then switched the CRS on the shapefile from the properties menu from NAD83 to the same US Equal Area Conic and tried to calculate again with the same results. Do I need to make a copy of the shapefile and set to the CRS that way? Or am I doing something else wrong?