Hardness conversion

45 HRC is roughly 446 HV, 421 HBW, and about 1480 MPa (215 ksi) tensile strength for non-austenitic steel, per ASTM E140 and ASTM A370. This page converts between Rockwell C (HRC), Vickers (HV), Brinell (HBW 10/3000, 3000 kgf), and approximate tensile strength — type a value and scale, and it prints the seven-row window around your value.

Cross-scale hardness conversions are approximate by definition: the scales measure different indentation responses, so treat converted values as indicative (±1–2 HRC is typical), not certified. The tensile columns are estimates and are omitted above roughly 48 HRC where the correlation breaks down.

Rockwell C · ASTM E18

45 HRCexample

Time not to scale

HRC = N - \frac{h}{S} = 100 - \frac{h}{0.002 mm}

h = (100 - 45) \times 0.002 = 0.110 mm

HRC = 100 - \frac{0.110}{0.002} = 45

F = F_{0} + F_{1} = 10 + 140 = 150 kgf

ASTM E140 Table 1

Type a hardness to read it across the table.

Brinell HBW 10/3000 · ASTM E10

421 HBWexample

Time not to scale

d = \frac{d _{1} + d _{2}}{2} = 2.978 mm, \frac{d}{D} = 0.2978

HBW = \frac{0.102 \times 2 F}{π D ( D - D ^{2} - d ^{2} )}

HBW = \frac{0.102 \times 2 \times 29420}{π \times 10 ( 10 - 10 ^{2} - 2.978 ^{2} )} = 421

How it’s calculated

No formula links the scales: Rockwell reads a depth under load, Brinell a ball indent's diameter and Vickers a pyramid's diagonal, each worked beside its drawing. The conversion is ASTM E140 Table 1, an empirical table for non-austenitic steels, read at the nearest row and never interpolated. Tensile strength is ASTM A370's approximate table, given up to 48 HRC. Brinell stops at ASTM E10's 650 HBW: the 60 HRC row's 654 is bracketed, for comparison only.

Which test when

	Rockwell	Brinell	Vickers
What is read	Depth h under F0, on the machine's dial	Indent diameter d, with a microscope	Indent diagonals d1, d2, with a microscope
Forces	F0 10 kgf; F 60, 100 or 150 kgf (C 150)	1–3000 kgf; 3000 kgf on a 10 mm ball for steel	1 gf to 120 kgf (E384 micro to E92)
Materials	C: hardened steel, 20–70 HRC. B: softer steel, brass	Soft to medium, to 650 HBW; castings, forgings, coarse grain (the big indent averages it)	Any metal, soft to very hard; thin parts, cases, coatings
Surface damage	Small, about 1 mm across	Large, 2.4–6 mm across with the 10 mm ball	Tiny, 0.02–1.4 mm; needs a ground or polished surface
Speed	Fastest: seconds, no optics	Slower: 10–15 s dwell, then optical reading	Slower: 10–15 s dwell, then optical reading

How accurate are hardness conversions?

Rockwell, Vickers, and Brinell each load a different indenter in a different way, so there is no exact algebraic relationship between them — the conversions come from empirical correlation tables (ASTM E140) built for a defined material class, here non-austenitic steels.

Expect agreement to about ±1–2 HRC. Brinell stops at 650 HBW, the top of the ASTM E10 range: the 60 HRC value is shown bracketed, for comparison only, and harder rows show —. The tensile column is ASTM A370’s approximate table, shown up to 48 HRC and as — above, rather than guessed. None of it applies to austenitic stainless, nickel alloys, titanium, aluminium or copper alloys.