This practice covers the application of the International System of Units (abbreviated SI) within the field of pulp, paper, and paperboard. The SI units have been adopted by ISO, ASTM, and TAPPI as the preferred units for use in their standards and test methods. Details of SI are given in various parts of ISO Standards 31 and 1000, and in ASTM Practice E 380. Application of this information is not always easy, as some properties cannot at this time be expressed in SI, some can be expressed in various units all within SI, and various multiples can be used. Such variation can lead to confusion in reporting test results and in quoting values for properties. In order to overcome such problems within the pulp, paper, and paperboard field, ISO/TC6 has recommended appropriate units in ISO Standard 5651. These recommendations are reproduced in this practice, together with other information and recommendations.