About this tool
The Hardness Conversion Calculator converts a single hardness reading between the common scales used for steel — Rockwell C (HRC), Rockwell B (HRB), Brinell (HB), Vickers (HV) and Knoop (HK) — and estimates the approximate ultimate tensile strength. Pick the scale you measured on, type the value, and it returns the equivalent value on every other scale at once. All the math runs locally in your browser, so nothing you enter is uploaded.
The tool stores the standard ASTM E140 / SAE J417 correspondence table for non-austenitic (hardened and tempered) steels and linearly interpolates between the tabulated rows. Internally it converts your input to a Vickers (HV) pivot, then reads across to each other scale and to the tensile column; where a scale is not defined for a given hardness — Rockwell C below about 20 HRC, Rockwell B above 100 HRB, or Brinell above roughly 650 HB — that cell shows a dash rather than an invented number. Tensile strength is reported in both MPa and ksi and, as a rough cross-check, follows the classic rule that ultimate tensile ≈ 3.4 × HB in MPa.
As a worked example, 45 HRC converts to about 446 HV, 421 HB and roughly 1450 MPa (210 ksi) tensile strength. These conversions are approximate and material-specific: they are calibrated for carbon and low-alloy steels and should not be applied to austenitic stainless, non-ferrous metals, or case-hardened surfaces, where the scale relationships differ. Use them as an engineering estimate, not a substitute for a test on the actual alloy.