# 49 CFR 171.10 - Units of measure.

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§ 171.10 Units of measure.
(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
Measurement SI to U.S. standard U.S. standard to SI
Abbreviation for units of measure are as follows:
Unit of measure and abbreviation:
(SI): millimeter, mm; centimeter, cm; meter, m; gram, g; kilogram, kg; kiloPascal, kPa; liter, L; milliliter, mL; cubic meter, m3; Terabecquerel, TBq; Gigabecquerel, GBq; millisievert, mSv; Newton, N;
(U.S.): Inch, in; foot, ft; ounce, oz; pound, lb; psig, psi; gallon, gal; cubic feet, ft 3; Curie, Ci; millicurie, mCi; millirem, mrem.
Activity 1 TBq=27 Ci 1 Ci=0.037 TBq
Length 1 cm=0.3937008 in1 m=3.280840 ft 1 in=2.540000 cm1 ft=0.3048000 m
Thickness 1 mm=0.03937008 in 1 in=25.40000 mm
Mass (weight) 1 kg=2.204622 lb1 g=0.03527397 oz 1 lb=0.4535924 kg1 oz=28.34952 g
Pressure 1 kPa=0.1450377 psi1 Bar=100 kPa=14.504 psi 1 kPa=7.5 mm Hg 1 psi=6.894757 kPa1 psi=0.06895 Bar
Radiation level 1 Sv/hr=100 rem/hr 1 rem/hr=0.01 Sv/hr
Volume (liquid) 1 L=0.2641720 gal1 mL=0.03381402 oz 1 m3=35.31466 ft3 1 gal=3.785412 L1 oz=29.57353 mL 1 ft3=0.02831685 m3
Density 1 kg/m3=0.06242797 lb/ft3 1 lb/ft3=16.01846 kg/m3
Force 1 Newton = 0.2248 Pound-force 1 Pound-force=4.483 N
[Amdt. 171-111, 56 FR 66159, Dec. 20, 1991, as amended by Amdt. 171-136, 60 FR 49108, Sept. 21, 1995; Amdt. 171-135, 60 FR 50302, Sept. 28, 1995; 66 FR 33335, June 21, 2001; 66 FR 45378, Aug. 28, 2001; 68 FR 75740, Dec. 31, 2003]

Title 49 published on 2013-10-01

The following are only the Rules published in the Federal Register after the published date of Title 49.

For a complete list of all Rules, Proposed Rules, and Notices view the Rulemaking tab.

• 2014-09-16; vol. 79 # 179 - Tuesday, September 16, 2014
1. 79 FR 55403 - Hazardous Materials: Emergency Restriction/Prohibition Order
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DEPARTMENT OF TRANSPORTATION, Federal Motor Carrier Safety Administration
Emergency Restriction/Prohibition Order.
The Emergency Restriction/Prohibition Order became effective on August 14, 2014.
49 CFR Part 109

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United States Code
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Title 49 published on 2013-10-01

The following are ALL rules, proposed rules, and notices (chronologically) published in the Federal Register relating to 49 CFR 171 after this date.

• 2014-09-25; vol. 79 # 186 - Thursday, September 25, 2014
1. 79 FR 57494 - Hazardous Materials: Reverse Logistics (RRR).
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DEPARTMENT OF TRANSPORTATION, Pipeline and Hazardous Materials Safety Administration
Notice of proposed rulemaking. Extension of comment period.
The comment period for the NPRM published August 11, 2014, at 79 FR 46748, is extended from October 10, 2014, until November 10, 2014. To the extent possible, PHMSA will consider late-filed comments.
49 CFR Parts 171 and 173