How to convert HBW to HRC for steel

How do you convert Brinell hardness, H B W, to Rockwell C, H R C? For a suitable steel, three hundred Brinell is roughly thirty-two Rockwell C. But this is an estimate between different tests, not an exact unit conversion. The material and the conversion table matter.

Brinell presses a tungsten carbide ball into the surface. After removing the load, the diameter of the impression helps determine the hardness. Rockwell C uses a diamond indenter and measures the permanent increase in penetration depth after loading. Both probe resistance to indentation, but they do not measure exactly the same response. That is why a universal multiplier cannot connect the scales.

Start by identifying the material and its condition. Our example uses a table for non-austenitic steels, including appropriate carbon and alloy steels. Find the Brinell column and the Rockwell C column. Do not accidentally read Rockwell A or B: those are different scales. Use the table that fits the actual material, not just a similar-looking number.

The reference table pairs three hundred one Brinell with thirty-two Rockwell C. Read across the same row: the two numbers describe an approximate hardness equivalence for that steel family. As a check, thirty-two in the Rockwell C column takes you back to three hundred one in the Brinell column.

What if the measured Brinell value is three hundred? It lies between two hundred ninety-four, paired with thirty-one, and three hundred one, paired with thirty-two. The Brinell gap is seven. Three hundred is six above the lower entry, so it is six sevenths of the way across. A local linear interpolation gives thirty-one plus six sevenths, or about thirty-one point eight six.

Those decimals describe the arithmetic, not the accuracy of the conversion. Report this example as about thirty-two Rockwell C. A fitted curve may give a slightly different decimal, but that does not make it an exact measurement. The useful check is that the estimate stays between thirty-one and thirty-two before rounding. A lookup and an interpolation should agree at the stated precision.

Do not carry this steel relationship over to aluminum, brass, or austenitic stainless steel without an appropriate conversion. Alloy, heat treatment, and structure can change the relationship. Stay within the usable table range, and do not extend the last line indefinitely. When a specification requires Rockwell C test results, follow the required test and acceptance rules rather than treating a conversion as a substitute.

The method is simple: identify the material, choose the matching conversion reference, read the correct columns, and interpolate only within a valid local interval when needed. Keep the approximation visible and round sensibly. In our steel example, three hundred Brinell corresponds to about thirty-two Rockwell C, with the table and material assumptions attached.