Guide for the Use of the International System of Units (SI)

2.1.1 Tables and graphs 
 
In tables, values of quantities expressed in acceptable units and the corresponding values expressed 
in other units may be shown in parallel columns, with the acceptable-unit column preceding the other-unit 
column. In graphs, axes labeled in other units shall be given secondary status. This may preferably be done 
by placing scale marks on and labeling the left-hand ordinate and bottom abscissa in acceptable units, and 
placing scale marks on and labeling the right-hand ordinate and top abscissa in other units. Alternatively, 
lighter-weight scale marks and smaller type may be employed to indicate other units using the same 
ordinate and abscissa as is used for the acceptable units. 
2.2 Descriptive information 
 
Descriptive information characterizes arrangements, environments, the generalized dimensions of 
objects, apparatus, or materials, and other attributes that do not enter directly into calculations or results. 
When necessary for effective communication, such information may be expressed using customary terms 
that are widely used and recognized. Examples include common drill sizes and traditional tools used in the 
United States, U.S. standard fastener sizes, commercial pipe sizes, and other common terms used in the 
trades, the professions, the marketplace, sports, and various social activities. When such descriptive 
information is given, values in acceptable units are not required. For example, it is permissible to refer to a 
“36-inch pipeline” or a “half-inch drill” without first giving the value in an acceptable unit. 
1
The NIST policy on the use of the SI is set forth in the NIST Administration Manual, Chapter 4, Communications, Subchapter 4.09, 
NIST Technical Communications Program, Appendix D—Use of Metric Units. 

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