Several federal agencies have already switched to SI units (a metric-based system of weights and measures) and have projects completed or underway using these units. Recently, many state transportation agencies also switched to SI units. And now local government agencies that depend on state concrete specifications will need to make the switch. To date, however, little attention has been paid to the details of how to build with concrete in a metric world. In particular, how will concrete be specified, ordered, manufactured, and tested under a metric system? Article provides a table of rational metric-conversion values to use when specifying, ordering, or testing concrete. The values are not simply soft conversions of current U.S. practice. They are hard conversions that provide metric equivalents in round numbers.