Hardness Conversion Chart (HRC, HV, HB, Tensile)

These conversions are approximate because each hardness test measures something slightly different: Rockwell C presses a diamond cone under a fixed load and reads penetration depth, Vickers uses a diamond pyramid and measures the indent's diagonal, and Brinell pushes a hard ball (here a 3000 kgf tungsten-carbide ball) and measures the impression width. Because the indenters, loads and geometries differ, the scales only correlate empirically — the relationship also shifts with alloy and microstructure, so a converted value can be off by a point or two of HRC. Brinell is left blank above roughly HB 650 (about HRC 60), where the ball flattens and the test is no longer valid, and the highest HRC rows omit tensile because SAE J417 stops tabulating it there. The tensile-strength column is a rule of thumb — for steel the ultimate tensile strength in MPa is roughly 3.45 × the Brinell number — and should never substitute for a real tensile test on a critical part.