AMERICAN NATIONAL STANDARD FOR PREFERRED NUMBERS

The purpose of this standard is to provide preferred numbers for use in standardization where a series of numbers is needed; for example, in sizes, capacities, power ratings, nominal diameters, or standard currents. It should be noted that these preferred numbers are independent of any measurement system and, therefore, can be used with metric or customary units. The series of preferred numbers are designated, respectively, R5,R10,R20,R40, and R80, where R stands for Renard and the number indicates the particular root of 10 on which the series is based. Additional derived series may be obtained by taking the terms at every second, third, or fourth step, etc, of the basic series. These derived series are designated R5/2,R10/3, etc. Methods of rounding the preferred numbers are included.