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Hardness Scale Converter (Mohs, Vickers, Brinell, Rockwell)

DeveloperMath

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INPUT

Auto Process

OUTPUT

Client Side

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Guide

Hardness Scale Converter

Convert a single hardness measurement across the Mohs, Vickers (HV), Brinell (HB), and Rockwell A / B / C scales in one click. The converter uses ASTM E140 lookup data (with linear interpolation between rows) for the steel scales, plus a log-linear fit between Mohs and Vickers so you can compare metals against minerals on the same chart.

The result panel also surfaces a “nearest common materials” list — quickly see whether your reading sits in the range of mild steel, hardened tool steel, quartz, or tungsten carbide. An out-of-range warning flags values that fall outside the standardized conversion tables so you do not silently extrapolate.

How to Use

Pick the source scale your reading is on — Vickers, Brinell, Rockwell A/B/C, or Mohs.
Enter the hardness value. The tool recalculates as you type.
Read the equivalent values on every other scale, each with a one-click copy button.
Check the nearest common materials panel for a quick sanity-check against real-world references.
If a result shows “out of typical range”, treat it as an extrapolation rather than a verified conversion.

Features

Six scales in one view — Mohs, Vickers (HV), Brinell (HB, 3000 kgf, 10 mm tungsten ball), Rockwell A (HRA), Rockwell B (HRB), Rockwell C (HRC).
ASTM E140 conversion table — uses the same standardized reference data engineers rely on for non-austenitic steels.
Mohs ↔ Vickers bridge — log-linear fit through the ten reference minerals (talc through diamond) so mineral and metal hardness can be compared.
Material reference list — five nearest everyday materials by Vickers hardness, recomputed as you type.
Range / regime indicator — labels the input as soft, medium, hard, very hard, or extremely hard, and warns when the value falls outside the standard conversion tables.
Pure client-side — runs entirely in your browser. No data is uploaded.
Copy any result — every converted value has a copy-to-clipboard button.

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 FAQ

Why are Mohs and Vickers values not linearly related?

The Mohs scale is ordinal — each step only means "can scratch the one below" and the spacing between minerals is uneven. Diamond (Mohs 10) is more than five times harder than corundum (Mohs 9) when measured in Vickers, even though they differ by only one Mohs step. That is why converters use a logarithmic curve fit through the reference minerals rather than a straight line.
What is ASTM E140 and why does it matter for steel?

ASTM E140 is the standard that publishes equivalent hardness numbers for steels and other metals across Brinell, Vickers, Rockwell, and Knoop. The conversions are empirical — derived from measuring the same specimens with multiple machines — and they explicitly apply to non-austenitic steels. Converting hardness on stainless, aluminum, or copper alloys with this table will produce numbers that look plausible but can be significantly off.
Why does Rockwell B not exist above ~110 HRB?

Rockwell B uses a 1/16 inch steel ball as the indenter under 100 kgf. On hard materials the ball itself deforms, so readings above the upper range become unreliable. Test labs switch to Rockwell C (a diamond cone at 150 kgf) for harder steels, and to Vickers or Rockwell A for the hardest carbides and ceramics.
Is Vickers the same on hard ceramics as on soft metals?

In principle yes — Vickers uses a diamond pyramid that can indent almost anything from lead to corundum, which is why HV is the most universal hardness measure. In practice the load and dwell time chosen affect the reading on very hard, brittle materials because cracking around the indent influences how the diagonal is measured.
How is hardness related to tensile strength?

For carbon and low-alloy steels, ultimate tensile strength in MPa is roughly 3.2 to 3.5 times the Brinell hardness number — this is the relationship ASTM A370 documents. The correlation breaks down for cold-worked metals, austenitic stainless steels, and non-ferrous alloys, so it should be used only as a rough estimate, never a structural design input.