To convert a Rockwell hardness number, find the value under the correct Rockwell column on a hardness conversion chart and move horizontally across the table until you reach the column with the desired units. Although though there is no such thing as a Rockwell hardness conversion chart, a hardness conversion chart can be used to convert a Rockwell hardness number to another unit. Hardness is a material characteristic that describes a material's ability to resist indentation.
The Rockwell hardness testing method is the most common hardness scale and applies a large force onto a tool called an indenter to leave an indentation in a material. The depth of the indentation correlates to the hardness of the material.
There are seven combinations of indenters and forces named A through G. For example, a Rockwell test type B applies a 100 kilogram force (kgf) on a 1/16th-inch diameter steel ball indenter. These test combinations A through G determine which Rockwell column to look under when referencing a hardness conversion chart. The Rockwell hardness number can be converted to Brinell, Vickers, Shore, and other hardness scales.
When conducting a Rockwell hardness test, scientists choose the combination with the largest force and smallest indenter appropriate for the material type and operation conditions. For brittle or very thin materials, a superficial Rockwell hardness test can be conducted that uses shallower indenters and smaller forces.