"Foreword- This report is designed to assist users of the SAE Handbook in conversion of dimensions and units of measure between the U.S conventional1 system and the metric2 system. The same accuracy is obtainable with either system of units. The difference is in the names and relationships only. The SAE Recommended Practice is consistent with conversion practices of ISO R370@ ASA@ and ASTM. The report includes the following: General Rules; Rules for Conversion from Inch to Metric; Rules for Converting form Metric to Inch; Rules for Rounding; Rules for Converting Toleranced Dimension; Rules for Temperature Scale Conversion; all with supporting tables@ Also included are useful tables for converting quantities and units of space@ mechanics@ electricity and light@ and reciprocal units. The term ""exactly"" has been used with all exact conversion factors. Conversion factors not so labeled have been rounded in accordance with the rounding procedures contained in this practice. 1U.S. conventional units refers to the customary U.S. Units such as inch@ foot yard@ mile@ pound (avdp)@ U.S. gallon and its subdivision. 2The metric units and conversion factors presented here are based on the ""International System of Units@"" commonly abbreviated ""SI"" fixed by the General Conference on Weights and Measures; this system is also known as the Giorgi or MKSA [meter-kilogram 9mass)-second-ampere] system. This system has been adopted by the International Organization for Standardization in ISO Recommendation R31."