Steel tools

Small calculators that answer the questions that come up next to a grade lookup.

Last updated 12 November 2026

Hardness conversion is an approximation, and the standard says so

Brinell, Rockwell and Vickers measure three different things: the diameter of a ball indentation, the depth of a cone penetration, and the diagonal of a diamond pyramid impression. There is no physical law connecting them, only empirical tables built from measurements on real material — ISO 18265 for the metric world, ASTM E140 in the American one.

That has two consequences worth stating plainly. The tables are material-specific: the carbon-steel column does not apply to austenitic stainless, aluminium or cast iron. And a converted value is never a substitute for a measurement — if a specification calls for 30 HRC, testing 285 HB and converting is evidence, not conformity.

• ISO 18265 table A.1 covers unalloyed and low-alloy steel and cast steel.

• Conversions are least reliable at the ends: below 20 HRC and above 60 HRC.

• Tensile strength from hardness is an estimate with a spread of roughly ±10 %.

• Always record the test method and scale, not just the number.

Weight from dimensions: one relation, six shapes

Every weight on the calculator is cross-sectional area multiplied by length multiplied by density. Carbon steel is taken at 7.85 g/cm³, austenitic stainless at 7.90–8.00, ferritic stainless at 7.70, and the grade selector changes that one number.

The shapes differ only in how the area is found: width × thickness for plate and flat bar, π/4 × d² for a round, a² for a square, 0.866 × a² across flats for a hexagon, and π/4 × (OD² − ID²) for a tube. Nothing else is involved, which is why the result can be checked by hand in a few seconds.

Material numbers are identifiers, not specifications

A Werkstoff number such as 1.4301 or a UNS designation such as S30400 identifies a material uniquely, which a grade name does not: "stainless 304" appears in half a dozen standards with different tolerances. The number resolves the ambiguity about which alloy is meant, and nothing more.

It does not carry the product form, the delivery condition, the surface finish or the mechanical requirement, and those are what a purchase order needs. A number lookup is the first step of a specification, not the whole of it — the grade page it leads to carries the composition limits, the equivalents in other systems and the standards that govern each product form.

Where these tools sit in a specification

The usual sequence runs in one direction. A drawing or a certificate gives a number or a foreign grade name; the lookup resolves it to a grade page; the grade page gives composition, mechanical properties and the equivalents; the hardness converter translates a hardness requirement between the scale on the drawing and the scale the test house uses; the weight calculator turns the finished dimensions into a mass for quotation and transport.

Each step is small. Taken together they are most of what stands between a foreign specification and an order that can be placed.

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