How this calculator works
Brinell, Vickers, Rockwell C and Rockwell B measure hardness in different ways. Brinell presses a hard ball into the metal and divides the load by the indentation area. Vickers uses a diamond pyramid. Rockwell measures the depth of penetration under a major load, with the C scale using a diamond cone and the B scale a steel ball. Because the methods respond differently to elastic recovery and work hardening, there is no exact universal conversion. The table used here is an approximate comparison for non-austenitic steels, and values between rows are interpolated linearly.
Formula
No single formula relates the scales. For an entered value between two reference rows, each other scale is interpolated as y = y1 + (x - x1) x (y2 - y1) / (x2 - x1). The bracketing rows are shown with the result. Values outside the tabulated range are rejected rather than extrapolated.
Worked example
200 HB is a table row that gives 199 HV, 16 HRC and 93 HRB. 40 HRC is a row that gives 370 HB, 385 HV and 112 HRB. A value between rows is interpolated linearly and is an estimate, not a measurement.
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Frequently asked questions
Why do different hardness scales need conversion tables?
Each test measures a different physical response. Brinell area and Rockwell depth do not map onto each other by a fixed formula across materials, so conversions come from measured comparison tables rather than a physical law.
Is this valid for stainless steel or aluminium?
No. The table applies to non-austenitic steels such as carbon, alloy and tool steels. Austenitic stainless steels work-harden strongly, and aluminium, brass and nickel alloys need their own tables in ASTM E140 or ISO 18265.
How accurate is an interpolated value?
It is an estimate between published approximate rows. ASTM E140 warns that converted hardness is approximate and should be used only when a direct test is impossible. Treat the result as a few units, not a precise measurement.