Because federally funded construction projects are now required to be designed in metric units and built with metric materials, mills are reducing and will eventually eliminate their output of inch-pound bars and produce soft metric bars instead. Fortunately, the use of soft metric rebar will not require changes in design or in fabrication and construction practices, since soft metric rebar are physically the same size as corresponding inch-pound bars. It will be important, however, for designers and contractors to become familiar with the specifications of the new metric bar sizes.

ASTM specifications for reinforcing bars adopted soft metric bar sizes in 1996. This article includes tables comparing the differences in ASTM size designations, diameters, cross-sectional areas and weights for soft metric and inch-pound bars. In addition to these differences, other differences in the ASTM metric provisions for rebar include:

  • Minimum yield strengths, or grades
  • Bar marking
  • Substitution of metric bars for inch-pound bars