Hardness Conversion Calculator

They're reference-grade approximations. The relationship between hardness scales isn't a clean mathematical formula — it comes from empirical correspondence tables derived from real testing, most authoritatively standardized for steel in references like ASTM E140. This tool interpolates between sampled points from that kind of widely-published reference table. For tolerance verification or certification, you need an actual physical hardness test on the relevant scale.

It's not recommended. These conversion tables are calibrated for steel. Other materials — aluminum, brass, plastics — have a different relationship between hardness and strength, so applying the same table to them can introduce significant error.

A standard Brinell test (especially with a common carbide-ball indenter) becomes unreliable on very hard materials — the indenter itself can deform, and results lose accuracy — so in practice Brinell isn't used much above roughly HB 500 (≈HRC 50). Harder materials are typically measured with Rockwell C or Vickers instead. This tool won't show an HB estimate in a range it isn't reliable.

Rockwell B is a separate scale used for comparatively soft materials — annealed mild steel, aluminum, brass. We couldn't find a reliably sourced table that bridges HRB directly to HRC/HV, so this tool only converts HRB to HB and doesn't chain it further. We'd rather narrow the scope than fabricate a bridge we're not confident in.

The tool shows a clear out-of-range message instead of a number. We'd rather be upfront about not covering that range than invent a number from data we don't actually have.