2 C.F.R. § 700.6 Metric system of measurement.
(a) The Metric Conversion Act, as amended by the Omnibus Trade and Competitiveness Act (15 U.S.C. 205) declares that the metric system is the preferred measurement system for U.S. trade and commerce.
(b) Wherever measurements are required or authorized, they must be made, computed, and recorded in metric system units of measurement, unless otherwise authorized by the Agreement Officer in writing when it has been found that such usage is impractical or is likely to cause U.S. firms to experience significant inefficiencies or the loss of markets. Where the metric system is not the predominant standard for a particular application, measurements may be expressed in both the metric and the traditional equivalent units, provided the metric units are listed first.