(a) General. To ensure compatibility with international transportation standards, most units of measure in this subchapter are expressed using the International System of Units (“SI” or metric). Where SI units appear, they are the regulatory standard. U.S. standard or customary units, which appear in parentheses following the SI units, are for information only and are not intended to be the regulatory standard.
(b) Abbreviations for SI units of measure generally used throughout this subchapter are as shown in paragraph (c) of this section. Customary units shown throughout this subchapter are generally not abbreviated.
(c) Conversion values.(1) Conversion values are provided in the following table and are based on values provided in ASTM E 380, “Standard for Metric Practice”.
(2) If an exact conversion is needed, the following conversion table should be used.
Table of Conversion Factors for SI Units
SI to U.S. standard
U.S. standard to SI
1 TBq=27 Ci
1 Ci=0.037 TBq
1 cm=0.3937008 in1 m=3.280840 ft
1 in=2.540000 cm1 ft=0.3048000 m
1 mm=0.03937008 in
1 in=25.40000 mm
1 kg=2.204622 lb1 g=0.03527397 oz
1 lb=0.4535924 kg1 oz=28.34952 g
1 kPa=0.1450377 psi1 Bar=100 kPa=14.504 psi1 kPa=7.5 mm Hg