Enter hardness data
Supported engineering scales
Vickers, Brinell, Rockwell C, Rockwell B, Rockwell A, Knoop, and Mohs. Results come from interpolated reference points and should be treated as approximate.
Example data table
| Input | Reference | Brinell | Rockwell B | Rockwell C | Knoop | Mohs |
|---|---|---|---|---|---|---|
| 120 HV | Vickers | 114 HBW | 67.00 HRB | N/A HRC | 128.80 HK | 3.67 Mohs |
| 250 HV | Vickers | 238 HBW | 100.00 HRB | 23.68 HRC | 265.00 HK | 5.22 Mohs |
| 450 HV | Vickers | 428 HBW | N/A HRB | 46.00 HRC | 478.00 HK | 6.85 Mohs |
| 800 HV | Vickers | 760 HBW | N/A HRB | 64.00 HRC | 848.00 HK | 8.00 Mohs |
These rows demonstrate the calculator style only. Exact laboratory conversions vary by alloy, heat treatment, indenter, and test standard.
Formula used
Hardness scale conversion is handled with piecewise linear interpolation between tabulated reference points. The calculator first converts the source value to an internal Vickers-equivalent value, then converts that Vickers value to every supported target scale.
Interpolation between two reference points
y = y1 + ((x - x1) / (x2 - x1)) × (y2 - y1)
For source-to-Vickers conversion, the same interpolation is applied to the reversed lookup table. This means the selected source scale becomes the interpolation axis, while Vickers becomes the solved value.
Optional steel strength estimate
UTS (MPa) ≈ 3.45 × HBW
This tensile relation is a screening approximation for many steels. It should not replace tensile testing, certification, or material acceptance standards.
How to use this calculator
- Select the hardness scale used by your original test.
- Enter the measured value from the instrument or report.
- Choose a primary target scale or keep the all-scale overview.
- Set decimal places for reporting precision.
- Pick linear interpolation for smooth estimates or nearest point for quick table-style matching.
- Set an uncertainty band to visualize a practical result spread.
- Enable the steel strength estimate only when Brinell-based screening is useful.
- Submit the form and review the result table, chart, and export buttons.
FAQs
1) Are hardness scale conversions exact?
No. They are empirical approximations based on reference tables and interpolation. Real conversion differences come from material type, surface condition, indenter geometry, applied load, and heat treatment history.
2) Why does one scale show unavailable?
Some scales only cover limited hardness bands. For example, Rockwell B is intended for softer materials, while Rockwell C is usually used for harder steels. Outside those ranges, the calculator marks the result unavailable.
3) Which interpolation mode should I choose?
Linear interpolation is better for smooth estimated conversions between known points. Nearest-point mode is useful when you want a quick lookup that behaves more like a fixed table.
4) Is Mohs suitable for precision engineering control?
Usually no. Mohs is a scratch hardness scale and is far less precise than indentation methods such as Vickers, Brinell, or Rockwell. It is better for broad comparison than formal quality control.
5) Can I estimate tensile strength from hardness?
Yes, but only approximately and mainly for many steels. The calculator uses a simple Brinell-based relation for quick screening. Final design, safety, and certification decisions still require actual tensile data.
6) Why use Vickers as the internal reference?
Vickers spans a broad hardness range and works well as a common internal bridge. Converting to one anchor scale first simplifies mapping to several target scales using the same interpolation workflow.
7) Does alloy type affect conversion accuracy?
Yes. Material composition, microstructure, and heat treatment can change how closely one hardness scale corresponds to another. The same nominal hardness may not convert identically across very different alloys.
8) When should laboratory values override this tool?
Always use laboratory or certified production measurements for contracts, audits, design approval, code compliance, failure analysis, and final inspection. This calculator is intended for engineering comparison and planning support.