Hardness Conversion.
Convert between Rockwell C (HRC), Rockwell B (HRB), Vickers (HV), Brinell (HB), Knoop (HK), and tensile strength. Based on ASTM E140 standard conversion table for steels.
Pick input scale
Equivalent values
Common reference points
| Material / Condition | HRC | HV | HB | UTS (MPa) |
|---|---|---|---|---|
| Mild steel — annealed | — | 120 | 114 | 390 |
| EN8 — normalised | 20 | 240 | 228 | 790 |
| EN24 — Q&T | 32 | 319 | 304 | 1050 |
| Spring steel — tempered | 45 | 446 | 424 | 1465 |
| Tool steel D2 — hardened | 60 | 697 | — | 2400 |
| HSS M2 — hardened | 64 | 800 | — | 2750 |
| Carbide insert | 72+ | 1500+ | — | — |
Hardness Scales and Conversion
Material hardness is tested using several different scales depending on material type, sample geometry, and required precision. Converting between scales lets you compare specs across drawings and material certificates.
Common Hardness Scales
- HRC (Rockwell C) — Hard steels, tool steels, hardened bearings. Range: 20-65 HRC.
- HRB (Rockwell B) — Soft steels, brass, aluminum. Range: 0-100 HRB.
- HB (Brinell) — Castings, forgings, large samples. Range: 50-650 HB.
- HV (Vickers) — Microhardness, thin sections, coatings. Range: 5-3000 HV.
- Shore A / D — Rubber, plastics, elastomers.
How Hardness Tests Work
Each scale presses a specific indenter (diamond cone, ball, or pyramid) into the sample with a fixed load, then measures the indentation:
- Rockwell — measures depth of penetration after preload.
- Brinell — measures diameter of spherical indentation.
- Vickers — measures diagonal of pyramidal indentation.
Hardness vs Tensile Strength
For carbon steels, there's a useful approximate relationship:
UTS (MPa) ≈ HB × 3.45 (for steel, HB < 400)
So a steel at 200 HB ≈ 690 MPa UTS. This breaks down for very hard steels (above ~50 HRC) where the ratio drops.
Typical Hardness Ranges for Manufacturing Materials
- Aluminum 6061-T6: 95 HB
- Brass C36000: 95-100 HB
- Mild steel C1018: 130 HB (annealed)
- Medium carbon C1045 (normalized): 200 HB
- Tool steel D2 (hardened): 58-62 HRC
- Hardened bearing steel 52100: 60-64 HRC
- Stainless 304 (annealed): 70 HRB
- Stainless 17-4PH (H900): 44 HRC
Hardness Test Considerations
- Sample thickness — too thin and the anvil affects reading. Rule: thickness ≥ 10× indentation depth.
- Surface preparation — heat-treatment scale or oxide layer falsifies readings. Grind clean.
- Edge effects — minimum 2.5× indentation diameter from edge.
- Conversion error — converted values are approximate. For specs, test with the specified scale directly.
Related Tools
For material identification and weight calculations, see Material Weight Calculator. Document hardness on FAI in AS9102 Form 3. For PPAP material verification, see PPAP Submission Checklist Element 9.