How it works
Hardness methods measure different things: Brinell the ball impression diameter, Vickers the diagonal of a diamond pyramid impression, Rockwell the indentation depth of a cone. There is no exact formula between them, so conversion uses tables consistent with ASTM E140 and ISO 18265. The calculator interpolates between 1 HRC rows.
Tensile strength of steel is estimated as Rm ≈ 3.4 x HB MPa. It is a guide for carbon and low-alloy steels, not a substitute for a tensile test.
HRC - HV - HB conversion table for steel
| HRC | HV | HB |
|---|---|---|
| 20 | 238 | 226 |
| 30 | 302 | 286 |
| 35 | 345 | 327 |
| 40 | 392 | 371 |
| 45 | 446 | 421 |
| 50 | 513 | 481 |
| 55 | 595 | 560 |
| 60 | 697 | - |
| 65 | 832 | - |
Limits
- Steel only. For cast iron, non-ferrous alloys, case-hardened and hardfaced layers the error is large.
- Below 20 HRC the C scale does not apply - measure soft steel in HB or HRB.
- Above ~59 HRC Brinell is not used: the ball deforms on hardened steel.
- If the drawing specifies a method, inspect with that method.
Further reading
How the methods differ and typical hardness of common steels: Rockwell and Brinell hardness.