Enter a Brinell hardness (HB) for a steel and get approximate Vickers (HV), Rockwell C (HRC), and tensile strength estimates. These conversions follow the trends in ASTM E140 and SAE J417 but are approximate and material-specific — always confirm critical values against the published tables.
Hardness is the quickest, cheapest, and most non-destructive way to judge a metal's strength, and shops routinely need to translate between the Brinell, Vickers, and Rockwell scales — and on to an estimate of tensile strength. This calculator does exactly that for steels, using the well-known correlations behind ASTM E140 and SAE J417. Every output is clearly labelled approximate: hardness conversions depend on the material and processing, and only the published standard tables are authoritative.
Brinell (HB) presses a hardened ball into the surface under a heavy load and measures the indentation diameter — averaging over a large area, it suits coarse, heterogeneous materials like castings. Rockwell C (HRC) measures the depth of penetration of a diamond cone under a defined load and reads directly off the machine; it is fast and dominant for hardened steels. Vickers (HV) uses a pyramidal diamond and the diagonal of the impression; it spans the widest hardness range and works on thin sections and small parts.
Because each method probes the material differently, conversions between them are empirical, not exact.
For steels of moderate hardness the Vickers and Brinell numbers are nearly equal, HV ≈ HB, because both are defined as load over indentation area and use similar mechanics. This approximation holds well up to roughly HB 450 (≈ HV 450).
Above that, the Brinell ball begins to flatten and deform on very hard material, so HB under-reads and the two scales diverge — which is exactly why Brinell testing is not used above about 450–650 HB and Vickers or Rockwell C takes over. The calculator flags this divergence in the HV result.
Rockwell C is meaningful only for hard materials, roughly 20 HRC and above (about HB 230+). This tool uses a monotonic approximation, HRC ≈ 100 − 1.586×10⁴/HB, that follows the E140 trend over roughly HB 250–600 and is guarded outside that band, where it returns "—" rather than a misleading number.
Soft steels simply do not have a valid HRC value — they are measured on the Rockwell B scale instead. Treat any single-formula HRC as a first estimate; the standard tables include separate columns for non-austenitic steels, and the spread between sources can be a point or two.
For carbon and low-alloy steels there is a remarkably robust link between hardness and ultimate tensile strength: UTS (MPa) ≈ 3.45 × HB, equivalently UTS (psi) ≈ 500 × HB, or about 0.5 ksi per Brinell point. A steel at 200 HB therefore has roughly 690 MPa (100 ksi) tensile strength.
This correlation is one of the most useful rules of thumb in metallurgy — it lets a quick hardness check stand in for a destructive tensile test during incoming inspection or process control. It applies to steels; aluminium, copper, and other alloys follow different (and weaker) relationships.
They are estimates, typically good to within a few percent for the carbon and low-alloy steels they were derived from, but they can be off significantly for stainless, tool, austenitic, or non-ferrous materials. Conversions also drift near the ends of each scale. For any specification, acceptance, or safety-critical decision, use the ASTM E140 or SAE J417 tables for the specific material class rather than a formula.
That range covers where the Brinell test and its conversions are valid for steels. Below about 100 HB the material is very soft and Brinell loses resolution; above about 600 HB the steel ball deforms and Brinell is unreliable, so Vickers or Rockwell C is used instead. Inputs outside the range return "—" rather than an extrapolated, untrustworthy value.
Not reliably with this tool. The HV ≈ HB relation is broadly material-independent at moderate hardness, but the Rockwell C correlation and especially the hardness-to-tensile rule are calibrated for carbon and low-alloy steels. Austenitic stainless, aluminium, brass, and tool steels each need their own conversion data — use the appropriate ASTM E140 table.
Both hardness and tensile strength are governed by the same resistance to plastic flow. A hardness indentation is essentially a small, constrained compression test, so for a given metallurgical family the indentation pressure scales with the flow stress and hence the tensile strength. The constant (≈3.45 MPa or 500 psi per HB) captures that proportionality for steels.
No. Rockwell C uses a diamond cone and a heavy load suited to hard materials; on soft steel the indenter sinks too far and the reading is meaningless below about 20 HRC. Soft and medium steels are measured on the Rockwell B scale (HRB) with a ball indenter instead. That is why this calculator returns "—" for HRC when the Brinell value is too low.