Hardness Converter

Approximate steel correlations among Vickers, Brinell, Rockwell C, and a rough Shore D scale (not for acceptance testing).

Hardness scales are not units of the same quantity, they are separate indentation tests, so nothing here is a true conversion — it is a correlation, and only for steel. Vickers is the hub. Whatever you enter becomes an HV figure first, and the other three columns are rebuilt from it. Brinell is taken as HV divided by 1.02, a flat two percent offset reflecting how closely the two diamond-and-ball tests track through the middle of their range. Rockwell C is read from a fifteen-point ASTM E140-style table anchored at 250 HV to 23 HRC and rising to 940 HV at 68 HRC, with straight-line interpolation between anchors, which is how the default 450 HV arrives at 45.0 HRC and 441.2 HB. Both ends of that table misbehave in ways you should know. Below 250 HV the curve is extrapolated straight down to the origin, producing Rockwell C figures for soft material where the C scale is not valid at all — it bottoms out around 20 HRC in practice. Above 940 HV the readings stop moving: HRC holds at 68 and Shore D holds at 100 however much harder your entry claims to be. Shore D itself is a durometer scale built for rubber and plastics, fitted here to HRC by a crude linear expression, so read it as a ranking rather than a measurement. Aluminium, brass and cast iron follow different correlations entirely, and none of this is fit for acceptance testing against a specification.