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

B.3 Use of conversion factors 
 
Each entry in Secs. B.8 and B.9 is to be interpreted as in these two examples: 
To 
convert 
from 
to 
 
Multiply 
by 
atmosphere, standard (atm) ...........................pascal (Pa).......................................1.01325 ....................E+05 
cubic foot per second (ft
3
/s) ..........................cubic meter per second (m
3
/s) .........2.831 685 ................. E−02 
means
1 atm = 101 325 Pa (exactly); 
1 ft
3
/s = 0.028 316 85 m
3
/s. 
Thus to express, for example, the pressure p = 11.8 standard atmospheres (atm) in pascals (Pa), write 
p = 11.8 atm × 101 325 Pa/atm and obtain the converted numerical value 11.8 × 101 325 = 1 195 635 and 
the converted value p = 1.20 MPa. 
6
This appendix is essentially the same as Appendix B of the 1995 Edition. That appendix was significantly revised version of 
Appendix C of the 1991 Edition, which was reprinted from ANSI/IEEE Std 268-1982, 
American National Standard Metric Practice,
©1982 by the Institute of Electrical and Electronics Engineers, Inc., with the permission of the IEEE. The origin of this material is E. 
A. Mechtly, 
The International System of Units — Physical Constants and Conversion Factors
, NASA SP-7012, Second Revision, 
National Aeronautics and Space Administration (U.S. Government Printing Office, Washington, DC, 1973). 

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Guide for the Use of the International System of Units (SI) 
 
41 
Notes: 
1. Guidance on rounding converted numerical values of quantities is given in Sec. B.7.2.
2. If the value of a quantity is expressed in a unit of the center column of Sec. B.8 or B.9 and it is 
necessary to express it in the corresponding unit of the first column, divide by the factor. 
The factors for derived units not included in Secs. B.8 and B.9 can readily be found from the 
factors given.
Examples: To find the factor for converting values in lb·ft/s to values in kg·m/s, obtain from Sec. B.8 or 
B.9 
1 lb = 4.535 924 E−01 kg 
1 
ft 
=