Hardness Conversion Calculator

There is no exact conversion

Each scale presses a different indenter with a different load and measures the result differently. Rockwell C uses a diamond cone at 150 kgf and reads depth; Brinell uses a 10 mm ball at 3,000 kgf and measures the width of the dent; Vickers uses a diamond pyramid and works at almost any load.

Because they probe different volumes of material in different ways, converting between them is an empirical cross-reference built from measured data — the ASTM E140 tables — not an equation. Two materials with the same HRC can differ in HB.

What each scale is good for

• HRC — hardened steel, 20 to 68. Fast and non-destructive; the default for tool steel and heat-treated parts.
• HRB — softer steels, brass and aluminium, roughly 0 to 100. Overlaps HRC only slightly, around HRC 20.
• HB — castings and forgings. The large ball averages over a big area, which suits coarse or inhomogeneous material.
• HV — the widest range of all, and the only practical choice for thin sections, coatings and case-hardened layers.

The tensile strength column

For carbon and low-alloy steels there is a useful rule of thumb: tensile (MPa) ≈ 3.4 × HB. It is a correlation, not a law, and it does not hold for stainless, non-ferrous metals or work-hardened material. Never use it for a design calculation — test the actual alloy.

Values here are for steels and are interpolated between table points. Aluminium, copper alloys and stainless steels need their own conversion tables, and no table is valid outside the range where both scales were measured.