Formula for metric units
e1 = (12.74e0 ) / (Rm1 A1 ) 1/3
Formula for non-metric units
e1 = (144.2e0 ) / (Rm1 A1 ) 1/3
where:
e0 = Required thickness of the reference stainless steel in mm or inches respectively;
e1 = Equivalent thickness of the steel used in mm or inches respectively;
Rm1 = Specified minimum tensile strength of the steel used in deka-newtons per square millimeter or pounds per square inch respectively; and
A1 = Specified minimum percentage elongation of the steel used multiplied by 100 (for example, 20 percent times 100 equals 20). Elongation values used must be determined from a 50 mm or 2 inch test specimen.
49 C.F.R. §173.24b