How the hardness converter works
The calculator accepts one measured hardness value and asks two simple questions: what scale was the value reported in, and what scale do you want to see it in?
Once you answer those, it estimates an equivalent value in the target scale using lightweight empirical relationships that are easy to evaluate in a browser.
That makes the tool fast enough for quick checks while still being transparent about the underlying math.
Internally, the tool uses Brinell hardness as a bridge scale. If you enter a Vickers, HRB, or HRC number, the script first estimates the corresponding BHN value.
It then converts that internal BHN estimate to your requested output scale. This two-step structure keeps the calculator consistent from one conversion path to another and mirrors the way many printed shop references organize their tables.
How to use the converter
- Enter the measured hardness in Value. For example, enter 250 if a report says 250 BHN, or 60 if it says 60 HRC.
- Select the scale the value is currently reported in under From Scale.
- Select the desired output scale under To Scale.
- Select Convert. The result appears in the results panel and can be copied with Copy Result.
If you are checking several materials in a row, it helps to keep the original source scale written down beside each value.
The most common shop-floor mistake is not the arithmetic; it is accidentally treating an HRB number as HRC, or vice versa.
Recording the source scale prevents that mix-up and makes later reviews much easier.
Common hardness scales and what the symbols mean
Hardness values are dimensionless numbers derived from indentation tests. The result is meaningful only when you know the test method behind it.
The four scales in this calculator cover many everyday engineering situations in metals work, especially steels and related alloys.
- BHN (Brinell) uses a ball indenter and is often applied to castings, forgings, and general steel checks where a larger indentation is acceptable. It is useful when surfaces are not perfectly polished and when you want a broad indication of bulk hardness.
- HV (Vickers) uses a diamond pyramid and is common in laboratories, metallography, and microhardness work. Because Vickers can be used at many loads, it is flexible for both bulk materials and thinner sections.
- HRB (Rockwell B) is typically used for softer metals, mild steels, and some non-ferrous alloys. It is common where the Rockwell C scale would be too severe or too low in sensitivity.
- HRC (Rockwell C) uses a diamond cone and is widely used for hardened steels, tool steels, and case-hardened parts. It is one of the most familiar heat-treatment specification scales.
These tests all answer a similar question, but they do not probe the material in exactly the same way.
That is why the relationship between scales depends on the material family, microstructure, surface condition, and hardness range.
A conversion that is reasonable for a low-alloy steel may be less reliable for a cast iron, a heavily cold-worked stainless steel, a thin coating, or a part with a steep hardness gradient from surface to core.
Model and formulas used
The calculator uses simplified linear relationships that are convenient for quick engineering estimates. They are best treated as rule-of-thumb conversions, especially for many carbon and low-alloy steels in common working ranges.
The tool is intentionally transparent: you can reproduce every result with the formulas listed below.
Conversions to BHN as the internal step:
- From BHN: BHN = BHN
- From HV: BHN ≈ HV / 0.95
- From HRB: BHN ≈ 4.7 × HRB + 20
- From HRC: BHN ≈ 9.5 × HRC + 70
Conversions from BHN to the requested output:
- To HV: HV ≈ 0.95 × BHN
- To HRB: HRB ≈ (BHN − 20) / 4.7
- To HRC: HRC ≈ (BHN − 70) / 9.5
A useful way to read these equations is to see BHN as the shared middle language of the calculator.
That does not mean Brinell is somehow more fundamental than the other scales in all materials; it simply means the page uses BHN as a stable internal reference so that every conversion path is handled consistently.
Example formula (MathML)
One of the relationships used is the approximate conversion from Brinell to Rockwell C:
Worked examples
Worked examples are useful because they let you confirm not only the arithmetic but also your intuition. If the converted number lands far outside the range you expected for the material condition, that is a clue to re-check the source scale, the heat-treatment state, or the applicability of the estimate.
Example 1: Convert 250 BHN to HV, HRB, and HRC
Suppose a supplier datasheet lists a steel at 250 BHN. You want to compare that against a specification written in Vickers or Rockwell terms.
- To HV: HV ≈ 0.95 × 250 ≈ 237.5 HV.
- To HRB: HRB ≈ (250 − 20) / 4.7 ≈ 230 / 4.7 ≈ 48.9 HRB.
- To HRC: HRC ≈ (250 − 70) / 9.5 ≈ 180 / 9.5 ≈ 18.9 HRC.
The practical interpretation is that this is not extremely hard steel. A value around 19 HRC is compatible with many medium-strength conditions, but it would be far below what you expect from a hardened cutting tool or a heavily case-hardened wear surface.
Example 2: Convert 60 HRC to BHN and HV
Now consider a hard tool steel measured at 60 HRC. The calculator first estimates BHN, then converts to any requested output scale.
- HRC to BHN: BHN ≈ 9.5 × 60 + 70 = 570 + 70 = 640 BHN.
- BHN to HV: HV ≈ 0.95 × 640 = 608 HV.
That result sits in a much harder region than the previous example, which matches expectations for wear-resistant steels. If a high HRC input ever converts to a surprisingly low BHN or HV value, the first thing to check is whether the wrong Rockwell scale was selected.
Example 3: Common mistake check with HRB versus HRC
Rockwell B and Rockwell C are easy to confuse because both are often abbreviated as Rockwell hardness in conversation.
However, they serve different hardness ranges. As a quick plausibility check, 90 HRB can be reasonable for mild steel, while 90 HRC is generally unrealistic for steel.
If you accidentally treat 90 as HRC, the internal estimate becomes BHN ≈ 9.5 × 90 + 70 = 925, which should immediately look suspicious.
Sanity checks and typical ranges
These broad bands are not acceptance limits, but they are helpful for spotting obvious data-entry errors. Think of them as a quick gut-check for steels and similar engineering alloys.
- BHN: about 120 to 220 for many mild or structural steels, about 250 to 350 for stronger steels, and up into the 600 range for very hard surfaces or tool steels.
- HV: about 130 to 700 is common across many engineering steels, with higher values possible in special cases and coating work.
- HRB: roughly 40 to 100 for softer metals and mild steels.
- HRC: roughly 20 to 40 for many quenched-and-tempered steels, and about 50 to 65 for harder tool steels or case-hardened surfaces.
Another good sanity check is context. A drawing that calls for wear resistance, edge retention, or a hardened case should not usually convert into a very low hardness band.
On the other hand, a ductile formed part or low-carbon sheet product should not suddenly appear in a high-HRC region unless there is a special treatment involved.
Reference table
The table below uses the same formulas as the calculator, so the values are internally consistent with the page results. Published standards may differ because many official tables are non-linear and material specific.
This converter is intentionally simple so it stays fast and readable. That simplicity is a strength for quick estimates, but it also means you should understand where the result becomes less trustworthy.
This page is well suited to quick engineering estimates, classroom demonstrations, training discussions, and early-stage material comparisons.
It is not a substitute for a specified test procedure in a contract, a heat-treatment qualification program, or a formal acceptance inspection plan.
