How accurate are hardness conversions?

Conversions between hardness scales are approximate by nature because each test measures resistance to a different indenter under a different load. The ASTM E140 tables used here are the industry standard for carbon and low-alloy steel, and interpolating between rows keeps the error small, but treat the result as a reliable estimate rather than an exact measurement.

Why is a value sometimes shown as out of range?

Each hardness scale has a practical span. Rockwell C is meaningful for hardened steel from roughly 20 to 68 HRC, while Rockwell B suits softer material below about 100 HRB. If your input or its equivalent falls outside the valid window of a scale, the tool flags it rather than guessing a meaningless number.

Can I convert hardness to tensile strength?

For steel there is a well-established empirical link, so the tool estimates tensile strength in ksi and MPa from the Vickers value. This relationship does not hold for non-ferrous metals or stainless steel, and it is only an approximation even for steel, so do not use it for design without test data.

Do these conversions work for stainless steel or aluminum?

No. ASTM E140 has separate tables for austenitic stainless, nickel alloys, and other materials, and the scale relationships differ. This calculator uses the carbon and low-alloy steel table, so do not apply its numbers to stainless, aluminum, brass, or case-hardened surfaces.

What is the difference between Vickers and Brinell?

Vickers uses a diamond pyramid indenter and a small load, giving one continuous scale across soft and hard metals, which is why it works well as a master scale. Brinell presses a hardened ball under a heavy load and reads the indentation diameter, which suits coarse or non-uniform materials but flattens out on very hard steel.

Hardness Conversion Calculator

Hardness is measured several different ways, and shop drawings, mill certificates, and heat-treat specs rarely all use the same one. This calculator translates a value on one scale into its equivalents on the others for steel, so you can compare an HRC spec against a Brinell reading or a Vickers test without hunting through a printed chart.

How it works

Each hardness test pushes a different indenter into the surface under a different load, so there is no exact algebraic formula linking them. Instead, the industry relies on measured correlation tables. ASTM E140 publishes those tables for carbon and low-alloy steel, and this tool stores a condensed version with Vickers as the master column.

input value  ->  interpolate to Vickers (HV)
HV           ->  interpolate to HRC, HRB, HRA, HB
HV           ->  estimate tensile strength (ksi, then MPa)

When you enter a value, it is first converted to Vickers by linear interpolation between the nearest table rows, then Vickers is interpolated back out to every other scale. Any scale whose valid window does not include your value is marked out of range rather than extrapolated.

Tips and notes

These conversions apply only to carbon and low-alloy steels. Stainless steel, nickel alloys, and non-ferrous metals have their own ASTM E140 tables with different relationships, and case-hardened or surface-treated parts behave differently again.

The tensile strength estimate is a convenience, not a substitute for a tensile test. It follows the standard steel correlation but can be off by a noticeable margin depending on microstructure, so never use it as the basis for a structural calculation. For acceptance testing, always measure on the scale your specification calls out rather than converting from another.