---
title: "Hardness Conversion Chart: HRC, HRB, HB, HV | OpenSpindle"
description: "A steel hardness conversion chart mapping Rockwell C and B, Brinell, and Vickers, with approximate tensile strength, per ASTM E140 and SAE J417."
canonical: https://openspindle.com/reference/hardness-conversion-chart
---

# Hardness Conversion Chart

Convert between Rockwell C (HRC), Rockwell B (HRB), Brinell (HB), and Vickers (HV) hardness for steel, with approximate tensile strength, per ASTM E140.

Hardness gets specified and measured on different scales depending on the material and the tester, so drawings and datasheets often need conversion. This chart maps Rockwell C (HRC), Rockwell B (HRB), Brinell (HB), and Vickers (HV) for steel, plus the approximate tensile strength each level implies. The conversions are approximate and material-dependent: they are strictly valid for carbon and alloy steels (ASTM E140 / SAE J417), not for stainless, aluminum, or other alloys.

## Steel hardness conversion (HRC, HRB, HB, HV, tensile)

Rows run from hard to soft. Rockwell C covers hardened steel; Rockwell B covers softer steel and non-ferrous metals. Tensile strength is an approximation from Brinell hardness and should not be used for design.

| Rockwell C (HRC) | Rockwell B (HRB) | Brinell (HB) | Vickers (HV) | Approx. tensile (MPa / ksi) |
| --- | --- | --- | --- | --- |
| 60 | - | 654 | 697 | - |
| 55 | - | 560 | 595 | - |
| 50 | - | 481 | 513 | 1765 / 256 |
| 45 | - | 421 | 446 | 1510 / 219 |
| 40 | - | 371 | 392 | 1289 / 187 |
| 35 | - | 327 | 345 | 1125 / 163 |
| 30 | - | 286 | 302 | 965 / 140 |
| 25 | - | 253 | 266 | 835 / 121 |
| 20 | ~98 | 226 | 238 | 758 / 110 |
| - | 95 | 201 | 210 | 683 / 99 |
| - | 90 | 179 | 185 | 607 / 88 |
| - | 80 | 150 | 152 | 531 / 77 |

*Approximate values for carbon and alloy steel per ASTM E140 / SAE J417. Brinell is unreliable above ~650 HB, and the tensile approximation breaks down above ~50 HRC, so those cells are left blank.*

## Which scale to use

Rockwell C (HRC) is the standard for hardened tool steel, heat-treated parts, and case-hardened surfaces, typically from about 20 to 65 HRC. Rockwell B (HRB) covers softer steels, brass, aluminum, and annealed material. Brinell (HB) uses a larger indenter and suits castings, forgings, and coarse-grained material. Vickers (HV) uses a diamond pyramid and works across the full range, including thin sections and coatings, which makes it common in labs and on micro-hardness features.

## Why conversions are approximate

Each scale measures indentation differently, so there is no exact formula between them. Published conversions are empirical and were established for specific materials, chiefly carbon and alloy steels. Applying a steel conversion table to austenitic stainless, aluminum, or copper alloys can introduce meaningful error. When a hardness value is functionally critical, specify the scale and test method you actually want on the drawing rather than relying on a converted number.

Values reflect ASTM E140 and SAE J417 conversions for carbon and alloy steels. Conversions to and from other alloys are approximate. Confirm the required scale and test method with your shop before release.

## On OpenSpindle

- [Metal properties comparison](https://openspindle.com/reference/metal-properties-comparison.md)
- [Carbon steel machining](https://openspindle.com/materials/carbon-steel.md)
- [CNC machining](https://openspindle.com/capabilities/cnc-machining.md)

## Frequently asked questions

### How do I convert HRC to Brinell?

Use a standard steel conversion table (ASTM E140 / SAE J417). For example, 50 HRC is about 481 HB, 40 HRC is about 371 HB, and 30 HRC is about 286 HB. The conversion is approximate and valid for carbon and alloy steels, not for stainless or non-ferrous metals.

### Can I estimate tensile strength from hardness?

For steels, yes, approximately: tensile strength (psi) is roughly 500 times the Brinell hardness number. So a 300 HB steel is around 150,000 psi (about 1035 MPa). This is an estimate for carbon and alloy steel only and should not replace a real tensile test for design.

### What is the difference between Rockwell B and Rockwell C?

They use different indenters and loads. Rockwell B (HRB) uses a steel ball and suits softer steels and non-ferrous metals up to about 100 HRB. Rockwell C (HRC) uses a diamond cone and higher load for hardened steel, typically 20 to 65 HRC. The scales overlap only slightly around 20 HRC / 100 HRB.

### Are hardness conversions accurate for stainless or aluminum?

Only roughly. Standard conversion tables were established for carbon and alloy steels, so applying them to austenitic stainless, aluminum, or copper alloys introduces error. For those materials, measure on the scale you actually need rather than converting from another.