Hardness Conversion Formulas for Steel

Rockwell to Brinell (error expected to be +/- 10%) 
from "Indentation Hardness Testing" by V.E. Lysaght, p.134

For 40 < Rockwell B < 100

Brinell = 7300 / (130 - Rockwell B)

For 30 < Rockwell E < 100

Brinell = 3710 / (130 - Rockwell E)

For 10 < Rockwell C < 40

Brinell = (1520000 - 4500 Rockwell C) / (100 - Rockwell C)²

For 40 < Rockwell C < 70

Brinell = (25000 - 10 (57 - Rockwell C)² ) / (100 - Rockwell C)²

 

Hardness to Tensile Strength (error expected to be +/- 15%)
from "Indentation Hardness Testing" by V.E. Lysaght, p.134

For 82 < Rockwell B < 100

Tensile strength (psi) = (4750000 - 12000 Rockwell B) / (130 - Rockwell B)

For 10 < Rockwell C < 40

Tensile strength (psi) = 10⁵ (7000 - 10 Rockwell C) / (100 - Rockwell C)²

For Brinell < 175

Tensile strength (psi) = 515 Brinell

For Brinell > 175

Tensile strength (psi) = 490 Brinell

 

Depth of Penetration to Hardness
from "The Rockwell Hardness Test" by D.C. Van Aken

Rockwell B = 130 - depth of penetration (mm) / 2 mm

Rockwell C = 100 - depth of penetration (mm) / 2 mm