Brinell Hardness Number Calculator

Determine the indentation hardness of a material using the Brinell hardness number calculator.

Brinell hardness228.8 HBfrom a 3,000 kgf load on a 10 mm ball

Load-to-diameter-squared ratio30must match the material class for the result to be comparable — 30 for steel, 10 for copper alloys, 5 for aluminium

Indentation as a share of the ball40%within the valid 24–60% range

Estimated tensile strength789 MParoughly 3.45 × HB for steels — an empirical correlation, not a physical law, and it does not hold for non-ferrous alloys

In ksi114.4 ksiabout HB ÷ 2, the imperial rule of thumb

Approximate Rockwell Ctoo soft for the C scale — use HRB below about 229 HBinterpolated from published reference points, not a formula — there is no algebraic relation between the scales

Approximate Rockwell B98 HRBthe B and C scales overlap only narrowly, around 229–241 HB

Hardness scales are not interchangeableconversions are empiricaleach test loads the material differently, so published conversion tables are correlations fitted to particular alloy families and can be several points out on others

Against annealed aluminium9.151×about 25 HB

Against mild steel1.906×about 120 HB

Against hardened tool steel0.352×about 650 HB

The formula

HB = 2P ÷ (πD(D − √(D²−d²))); HV = 1.8544F ÷ d²

Hardness is a test result, not a material property

Unlike Young's modulus or yield strength, hardness is defined by the procedure used to measure it. Brinell presses a ball, Vickers a diamond pyramid, Rockwell measures depth rather than width. Each loads the material differently, so the numbers are not the same quantity and conversions between them are empirical correlations rather than exact relations.

Brinell has a further catch: the result depends on the load and ball size, so the ratio of load to diameter squared must match the material class — 30 for steel, 10 for copper alloys, 5 for aluminium — or two readings on the same metal will disagree. The indentation should also fall between 24% and 60% of the ball diameter; outside that the geometry stops being valid.

The correlation with tensile strength, about 3.45 MPa per Brinell point for steels, is genuinely useful for a quick estimate and genuinely approximate. It reflects that both properties depend on resistance to plastic flow, but it is a fitted relationship for ferrous alloys and does not carry over to aluminium or copper.