The OGF research & development department proudly presents our newest tool, the area size calculator:
http://tile.opengeofiction.net/util/relation_area.html
Just enter the relation ID into the "Relation" field at the bottom left corner, and hit "Enter". Alternatively, its also possible to enter the ogf:area, ogf:id or ref of a relation. If none of these matches, Nominatim will be queried for the name.
This tool is intended to replace the daily generated area table.