Hardness conversions are empirical relationships that are defined by conversion tables limited to specific categories of materials. This article summarizes hardness conversion formulas for various materials in a table. It tabulates the approximate Rockwell B and Rockwell C hardness conversion numbers for nonaustenitic steels. The article lists the approximate equivalent hardness numbers for Brinell hardness numbers and Vickers hardness numbers for steel in tables. The tables are also outlined in a graphical form.