Formula to convert brinell to rockwell?

To convert Brinell hardness (HB) to Rockwell hardness (HR), there is no direct formula, as the conversion depends on the specific materials and the Rockwell scale used (A, B, C, etc.). However, approximate conversion tables are commonly used in practice. For example, a typical conversion might suggest that a Brinell hardness of around 200 HB corresponds to approximately 100 HRB or 30 HRC, but these values can vary. It's always best to refer to specific conversion charts tailored to the materials in question for accurate results.