NIST Special Publication 1038: The International System of Units (SI) Conversion Factors for General Use

In 1988 Congress designated the International System of Units (SI), the metric system, as the preferred system of measurement for use in trade and commerce (15 U.S.C. §205 - 267). This publication provides guidance on the use of the International System of Units (SI) to ensure uniformity with the weights and measures usage in the commercial measurement system and in other applications. Government and industry use metric units for procurements, grants and other business-related activities, for educational information, and for guidance in publications. The practical guidance in this publication may be used for, but is not limited to, the drafting of laws, regulations, contracts, product specifications, purchase orders, and the preparation of public information, reports and brochures, correspondence, statistical tables, databases, and maps. In addition to serving as an authoritative document for the conversion of customary (inch-pound) units to metric, this publication also explains the relationship between metric units and inch-pound units.