Free Brinell to Rockwell calculator.
Instant, ASTM E140-compliant hardness conversions between Brinell (HB), Rockwell C (HRC), and Rockwell B (HRB), with tensile strength estimates. The precision tool trusted by injection molding professionals worldwide.
Brinell to Rockwell Hardness Converter
Valid input ranges: 111 to 739 HB, 1 to 65 HRC, 52 to 100 HRB. Values between table rows are linearly interpolated per ASTM E140.
Brinell to Rockwell Conversion Chart
| Brinell (HB) | Rockwell C (HRC) | Rockwell B (HRB) | Tensile (ksi) |
|---|
Showing the first 25 rows of the ASTM E140 reference table, from 739 HB (65 HRC) downward.
How the hardness
conversion works.
The Brinell hardness test presses a hardened steel or carbide ball into the material under a specific load, typically 3000 kgf for steels, and reads hardness from the indentation diameter. It excels at softer materials and gives excellent repeatability on large-grained or non-homogeneous stock.
The Rockwell test measures indentation depth instead. Rockwell C (HRC) uses a diamond cone indenter and is the standard for hardened tool steels above 20 HRC; Rockwell B (HRB) uses a 1/16 inch steel ball for softer materials. The scales overlap slightly between 20 and 30 HRC. A specialized Rockwell E scale covers bearing metals, plastics, and some aluminum alloys.
No formula perfectly correlates the scales, so the ASTM E140 standard publishes empirical tables from extensive testing of carbon and alloy steels. This calculator interpolates linearly between those data points, holding accuracy within ±2% for typical tool steels. For critical specs on tooling projects, always confirm with direct testing in the specified scale.
What the numbers mean
for your mold.
In injection mold manufacturing, steel hardness directly drives tooling longevity, surface finish quality, and production economics.
45 to 50 HRC
Standard production molds. Excellent balance of machinability and wear resistance. Suitable for 500K+ cycles with glass-filled materials.
50 to 55 HRC
High-wear applications. Required for abrasive materials like glass or mineral-filled resins. Expect 1M+ cycles before significant wear.
55 to 60 HRC
Premium tooling. Maximum wear resistance for critical surfaces, gates, and high-shear areas. Common in medical and optical applications.
28 to 35 HRC
Pre-hardened steels. Cost-effective for prototype and low-volume production. Easier machining but limited cycle life.
Pro tip from our engineers: when specifying offshore tooling, always request hardness verification certificates with both HRC and Brinell values. Dual-scale reporting helps catch measurement errors and ensures your tooling meets specification. Sizing a press too? Run the clamp force calculator next.
Hardness conversion questions, answered.
How accurate is this free Brinell to Rockwell calculator?
It uses ASTM E140 standard conversion tables with linear interpolation, providing accuracy within plus or minus 2% for carbon and alloy steels. For critical applications, we recommend direct hardness testing in the specified scale.
What's the difference between Rockwell C and Rockwell B scales?
Rockwell C (HRC) uses a diamond cone indenter and is designed for hardened steels above 20 HRC. Rockwell B (HRB) uses a 1/16 inch steel ball for softer materials like annealed steels and non-ferrous metals. The calculator supports both scales, which overlap slightly between 20 and 30 HRC.
Why do injection mold specifications use different hardness scales?
Different scales suit different materials and hardness ranges. Tool steel cores typically specify HRC (48 to 52 HRC is common), while softer components like aluminum cavity inserts might specify HRB. Using the appropriate scale ensures measurement accuracy.
What hardness do you recommend for injection mold tooling?
For standard production molds running unfilled resins, 48 to 52 HRC provides excellent wear resistance and machinability. For glass-filled or abrasive materials, we recommend 52 to 56 HRC. Contact our engineers to specify the optimal hardness for your application.
Can I use this calculator for stainless steel or aluminum?
ASTM E140 conversion tables are specifically validated for carbon and alloy steels. While the conversions may approximate other materials, use material-specific hardness data or consult with our engineers for non-ferrous specifications.
More free calculators on the engineering tools page. Need help specifying tool steel? Ask an engineer.
Hardness specs are just
the beginning.
MoldMinds manages every detail of your offshore tooling projects, from material selection and hardness verification to final T1 samples. Our engineering team ensures your molds meet specification, every time.