Hardness Conversion Calculator: Rockwell C, Vickers and Brinell for Steel, with Tensile Strength Estimate
Convert a hardness reading to the other scales and estimate the strength of the steel.
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How this calculator works
Choose the scale you have the reading on and enter the number.
The calculator interpolates the ASTM E140 conversion table for steel between the 20 to 60 HRC values to give the Rockwell C, Vickers and Brinell numbers.
It estimates the tensile strength as about 3.45 times the Brinell number (ISO 18265), and the yield strength of a quenched and tempered steel as about 0.85 of that.
Formulas used
- R_m \approx 3.45\,HBW\ \ (\mathrm{MPa})
Worked example
With the default numbers in the calculator above:
- Rockwell C hardness: 40.00 HRC
- Vickers hardness: 392.00 HV
- Brinell hardness (10 mm tungsten carbide ball, 3000 kgf): 371.00 HBW
- Estimated tensile strength of the steel (ISO 18265; about 3.45 times the Brinell number): 1279.95 MPa (about 185.64 ksi)
- Approximate yield strength for a quenched and tempered steel (about 0.85 of the tensile strength): 1087.96 MPa (a rough guide only)
Change the numbers in the calculator to see the full working, every step, for your own case.
Common questions
Which standards apply?
ASTM E140 for the conversion tables, ISO 18265 for the conversion of hardness values, and ISO 6506, 6507 and 6508 for the Brinell, Vickers and Rockwell tests.
How accurate is the conversion?
It is approximate and only for steel. The standards say a converted value is no substitute for a test on the scale that is needed.
Why does the table stop at 20 HRC?
Softer steels are read on the Rockwell B scale, or on the Brinell and Vickers scales, which are outside the table used here.
How is the tensile strength found from hardness?
For steel the tensile strength in megapascals is about 3.45 times the Brinell hardness number. It is a rough guide.
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Got a question about this? Ask an engineering question and get a plain-language answer with references.
Further reading: ASTM E140 Standard Hardness Conversion Tables for Metals; ISO 18265 Metallic materials: conversion of hardness values; ISO 6506-1, ISO 6507-1 and ISO 6508-1 (Brinell, Vickers and Rockwell hardness tests).
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