Inches or Millimeters?
NOTE: CRSI Board of Directors, through the Engineering Practice Committee, is encouraging producer Members to revert to an inch-pound bar marking system for all sizes and grades of deformed reinforcing steel products. The intention of this resolution is to reduce confusion and the chance of errors/delays from the construction supply chain. Click here to view the full resolution.
The sizes of soft metric reinforcing bars are the same as corresponding sizes of inch-pound bars. Soft metric bar designations are simply a relabeling of inch-pound unit bar designations.
Soft metric reinforcing bars are required to meet ASTM specifications, including identifying the producer's mill, bar size, type of steel, and minimum yield strength or grade, just like the inch-pound identification.
From the Manual of Standard Practice:
Engineering Data Report (EDR) 42: Using Soft Metric Reinforcing Bars in Non-Metric Construction Projects (PDF Download, myCRSI)
This report presents guidelines for using soft metric reinforcing bars on non-metric projects on which inch-pound dimensions and inch-pound reinforcing bars have been specified.
CRSI Manual of Standard Practice (Purchase Publication, myCRSI)
CRSI's Manual of Standard Practice is the definitive source of information about reinforcing bar sizes, technical specifications, bar markings, and other essential information about specifying, estimating, detailing fabricating, and placing reinforcing bars.
Currently, the inch-pound and the metric measurement systems co-exist throughout the U.S. construction industry. Starting in 1997, CRSI member steel mills took the initiative to convert to "soft metric" reinforcing bar production — which enables the industry to furnish the same reinforcing bars to inch-pound construction projects as well as to metric construction projects. This measurement system is used exclusively by mills and fabricators, and is never used on plans or in specifications.