Hardness Conversion Ratio

What is this formula?

The Hardness Conversion Ratio expresses the proportional relationship between two hardness values measured on different hardness scales. It is commonly used when comparing approximate hardness values obtained from Rockwell, Brinell, Vickers, Knoop, or other hardness testing methods.

When to use it

Use this formula when evaluating equivalent hardness values between different testing standards, comparing material specifications, or estimating hardness relationships during quality control and materials selection.

Example

A steel specimen has a hardness of 220 HB and an equivalent hardness of 23 HRC.

Data:

H1 = 220

H2 = 23

Formula:

HR = H1 / H2

Substitution:

HR = 220 / 23

Result:

HR = 9.57

The hardness value in the first scale is approximately 9.57 times the numerical value in the second scale.

Applications

- Materials testing laboratories

- Metallurgical quality control

- Heat treatment verification

- Comparison of hardness standards

- Engineering material selection

Note

Hardness scales are not linearly equivalent over their entire range. This ratio is only a simplified comparative indicator and should not replace official hardness conversion tables such as ASTM E140. Actual conversions depend on material type, hardness range, and testing method.