Calculator
This tool converts between common hardness scales and adds a steel-only tensile estimate. Results are interpolated from reference data, not a universal direct equation.
Plotly Graph
Reference mode shows scale relationships against Brinell hardness. Comparison mode shows the current converted set and excludes unavailable scales.
Formula Used
Hardness conversion tables are not perfectly linear across every material and test method. This calculator first estimates an equivalent Brinell hardness value, then derives the other scales from that reference value.
Piecewise interpolation:
y = y1 + (x - x1) × (y2 - y1) ÷ (x2 - x1)
Estimated tensile strength for steels:
UTS (MPa) ≈ 3.45 × HB
UTS (ksi) = UTS (MPa) ÷ 6.89476
Because the scales use different indenters and loads, conversions are best treated as engineering estimates. Certified test reports and formal standards remain the final authority.
How to Use This Calculator
- Enter the known hardness or tensile value.
- Select the source scale that matches your input.
- Choose the number of decimal places you want.
- Pick the graph style for either curves or result comparison.
- Submit the form to see the result cards above the calculator.
- Review the table, graph, and interpolation note for context.
- Use CSV or PDF buttons to export the current result set.
- Check the example table below for typical reference behavior.
Example Data Table
These example rows illustrate how the interpolated reference table behaves for typical Brinell inputs.
| Sample HB | Approx. HV | Approx. HRB | Approx. HRC | Est. UTS (MPa) |
|---|---|---|---|---|
| 120 | 127 | 64 | N/A | 414 |
| 180 | 193 | 85 | N/A | 621 |
| 240 | 258 | 96 | 19.0 | 828 |
| 320 | 348 | N/A | 31.0 | 1,104 |
| 500 | 548 | N/A | 50.0 | 1,725 |
Frequently Asked Questions
1. Is hardness conversion exact?
No. Conversion is an engineering estimate because hardness methods use different loads, indenters, and response curves. Material chemistry and heat treatment also affect the relationship between scales.
2. Which materials fit this calculator best?
It fits steel-focused reference behavior best, especially carbon and low-alloy steels. Stainless steels, cast irons, thin coatings, and nonferrous alloys may need separate certified conversion guidance.
3. Why do some scales show N/A?
Some converted values fall outside the usual working range for a scale. For example, low hardness values may not map meaningfully to HRC, while higher values may sit beyond typical HRB use.
4. How is tensile strength estimated?
The tensile estimate uses the common steel approximation UTS ≈ 3.45 × HB in MPa. That shortcut is convenient for quick screening, but it is not a substitute for an actual tensile test.
5. Why does the graph use reference curves?
Reference curves show how each scale changes across the Brinell range. They make nonlinear behavior easier to understand than a single raw converted number.
6. What is piecewise interpolation?
Piecewise interpolation connects two nearby reference points with a straight segment. The calculator finds your position between those points and estimates the missing value proportionally.
7. Can I enter decimal values?
Yes. The form accepts decimal inputs and lets you choose up to four decimal places for displayed results.
8. Should I trust one scale more than another?
Trust the scale that matches the original test method and material standard. Converted values are helpful for comparison, but the directly measured scale remains the stronger technical reference.