HRB to HRC Hardness Converter
Enter a Rockwell B hardness value (HRB) to estimate the equivalent Rockwell C value (HRC) for steel in the overlapping conversion range.
Recommended overlap input range: 82 to 100 HRB. Outside this range, direct HRB↔HRC conversion is not considered reliable.
What this HRB to HRC calculator does
This tool converts hardness values from the Rockwell B scale (HRB) to an estimated Rockwell C scale (HRC) value. It is built for quick engineering estimates, quoting discussions, and rough process checks when you need to compare hardness numbers from different specifications.
Because HRB and HRC use different penetrators and loads, they are not mathematically identical scales. The conversion is based on interpolation between commonly referenced steel conversion points in the overlapping range.
HRB vs HRC: what is the difference?
Rockwell B (HRB)
- Typically used for softer metals and softer steel conditions.
- Uses a 1/16-inch steel or carbide ball penetrator.
- Common in annealed, low-hardness, or lightly hardened materials.
Rockwell C (HRC)
- Used for harder steels and heat-treated parts.
- Uses a diamond cone (Brale) penetrator.
- Common in tools, hardened components, dies, and wear parts.
If a print says HRB and your customer asks for HRC (or the reverse), conversion charts are often used for communication. For acceptance testing and certification, always follow the specified test method directly.
How the calculator works
The script uses a small conversion table for steel and performs linear interpolation between data points. That means if your value falls between two known points, the tool estimates the in-between HRC value proportionally.
Example: if 94 HRB maps to 12 HRC and 96 HRB maps to 14 HRC, then 95 HRB is estimated as roughly 13 HRC.
Reference points used in this calculator
| HRB | Approx. HRC |
|---|---|
| 82 | 0 |
| 84 | 2 |
| 86 | 4 |
| 88 | 6 |
| 90 | 8 |
| 92 | 10 |
| 94 | 12 |
| 96 | 14 |
| 98 | 17 |
| 100 | 20 |
How to use this tool
- Measure or obtain your hardness value in HRB.
- Enter the number in the calculator.
- Click Convert to HRC.
- Read the estimated HRC output and use it as a practical reference.
Accuracy and limitations
Hardness conversion is always an approximation because material chemistry, microstructure, cold work, and heat treatment affect the relationship between scales. Two parts with the same HRB can produce slightly different HRC behavior depending on alloy and condition.
- Best used for carbon and alloy steels in overlapping ranges.
- Not recommended as a replacement for direct HRC testing on critical parts.
- Do not use estimated values as the sole basis for certification, conformance, or warranty decisions.
When to use direct testing instead of conversion
Use direct HRC testing when:
- A customer specification explicitly calls out HRC limits.
- The part is safety-critical or highly regulated.
- Material grade or heat treatment path is uncertain.
- You are close to upper or lower tolerance boundaries.
FAQ
Can I convert any HRB value to HRC?
Not reliably. Practical overlap is limited. This calculator is intentionally constrained to the range where an estimate makes sense for steel.
Why does the calculator show a warning outside range?
Outside overlap, HRB and HRC represent very different testing behavior. A numeric conversion can become misleading and should not be treated as valid.
Is this based on ASTM E140?
It follows the same practical idea of tabulated conversion and interpolation used in common industry references, but it is a simplified web estimate, not a replacement for official standards documents.
Can I use this for stainless steel, brass, or aluminum?
Use caution. Different materials can have different conversion behavior. For non-carbon/alloy steels, consult material-specific charts or direct test methods.