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Recommended Agency Procedures for
Implementing Federal Metric Policy
(NISTIR 4855)

May 1992

U.S. DEPARTMENT OF COMMERCE
Technology Administration
National Institute of Standards and Technology
Metric Program
Technology Services
Gaithersburg, MD 20899
James B. McCracken
Gary P. Carver

U.S. DEPARTMENT OF COMMERCE
Barbara Hackman Franklin, Secretary
TECHNOLOGY ADMINISTRATION
Robert M. White, Under Secretary of Technology
NATIONAL INSTITUTE OF STANDARDS
AND TECHNOLOGY
John W. Lyons, Director

Document Content:

  1. PURPOSE AND SCOPE

    The primary purpose of these recommended procedures is to assist federal agencies in their transition to the use of metric units ¹ in regulations, data
    requests, recordkeeping, and reports. Although this document is intended for federal use, it may also be useful to state and local government agencies
    and other organizations. The primary purpose of these recommended procedures is to assist federal agencies in their transition to the use of metric units ¹ in regulations, data requests, recordkeeping, and reports. Although this document is intended for federal use, it may also be useful to state and local government agencies and other organizations.

  2. BACKGROUND

    The policy of the United States, as stated by Congress,² is to require that each federal agency, by a date certain and to the extent economically feasible
    by the end of fiscal year 1992, use the metric system in contracts, grants and other business related activities. The federal Interagency Council on
    Metric Policy (ICMP)³ recommends that, in support of the national metric goals and the "Metric Conversion Policy for Federal Agencies" [1], federal
    agencies ensure;

    • That existing measurement-sensitive4 regulations or requirementsare amended as necessary to accommodate the transition to use ofthe metric system;
      and that metric units are the preferred units in new or revisedregulations or requirements.
    • That metric measurement expressions used are both meaningful5 values.

  3. REFERENCE DOCUMENTS

    There are a number of federal metric-related reference documents. These include the Executive Order on metric implementation [l], the interpretation of
    the metric system ill, guidance on using the metric system [2], and metrication in building design 131. Metric-related documents published by the
    General Services Administration (GSA) include a federal standard listing preferred metric and inch-pound units and conversion values for use with those
    units [4], metric usage requirements in the Federal Acquisition Regulations [5], guidance on using metric units in federal product descriptions [6],
    guidance on preparing metric construction designs [7], and guidance on using metric units in federal information processing [8]. Documents have also
    been published by the Departments of Defense and Agriculture, as well as other agencies. In the private sector there are also many current and
    authoritative documents, including metric guidance for the manager [9], metric editorial guidance [10], metric construction guidance [11], and
    information on metric training materials [12]. Many of the above documents list other useful reference documents.

  4. AGENCY ACTIONS

    1. When an agency implements preferred use of metric units,it should clearly define the policies, procedures,and conventionsinvolved in its implementation. Common understanding of the agency'sground rules is key to successful implementation of change.
    2. Agencies should be sensitive to the level of transitionof all parties affected by their planned actions, because many sectorsof the economy will differ in their approach to and/or willingnessto complete their transition to the use of metric units. Dependingon the extent of the use of metric units by affected parties, an
      agency might:
      1. Use metric units as the primary units in all measurement-sensitivetransactions. (For example, this would be done where an industryalready uses metric units exclusively or has clearly indicateda decision to do so.); or
      2. Use, on an interim basis, both metric and inch-poundunits while clearly indicating a policy of preferring metricunits with timetables and processes to achieve metric only usage.(For example, this might be done where an agency's measurement-sensitivemission needs cannot be met fully using available metric products.)
      In those cases where the sole use of metric units would compromisegood communication or other units have been specified as a contractualrequirement, quantifies should be expressed in metric unit followed,in parentheses, by the same quantities expressed in the other units.Exceptions may sometimes be necessary for commercial devices, technicalstandards, or quantities having special legal significance; examplesinclude commercial weights and measures devices and the relatedlaws and regulations. However, even in such cases, quantities expressedin metric units should be used whenever possible with the inch-poundunits following in parentheses.
    3. Agencies should be aware that the acceptability of particularmeasurement units to a given industry or sector may not be apparent.Therefore, it is important to ensure adequate opportunity for commentsby any affected industries, as well as the general public, on proposedchanges in the measurement units to be used. Federal Register notices,press releases, or the like should be used for this purpose.
    4. Federal metric policy [1] specifically prescribes thatagencies shall:
      1. Establish plans and dates for use of the metricsystem in procurements, grants and other business-related activities;
      2. Coordinate, through the ICMP, metric transition planswith other federal agencies, state and local governments, andthe private sector,
      3. Require maximum practical use of metric units inareas where federal procurement and activity represents a predominantinfluence on industry standards (e.g., weapon systems or spaceexploration.) Strongly encourage metrication in industry standardswhere federal procurement and activity is not the predominantinfluence, consistent with the legal status of the metric systemas the preferred system of weights and measures for United Statestrade and commerce;6
      4. Assist in resolving metric-related problems broughtto the attention of the agency that are associated with agencyactions, activities, or programs undertaken in compliance withthese guidelines or other laws or regulations;
      5. Identify measurement-sensitive agency policies,procedures,regulations, standards, specifications, procurements, and legislativeproposals and ensure that they are updated to remove barriersto transition to the metric system;
      6. Consider cost effects of metric use in setting agencypolicies, programs, and actions and determine criteria for theassessment of their economic feasibility. Such criteria shouldappropriately weigh both agency costs and national economicbenefits related to changing to the use of metric units;
      7. Provide for full public involvement and timely informationabout significant metrication policies, programs, and actions;
      8. Seek out ways to increase understanding of the metricsystem of measurement through educational information and guidanceand in agency publications;
      9. Consider, particularly, the effects of agency metricpolicies and practices on small business; and
      10. Consistent with the Federal Acquisition RegulationSystem (48 CFR), accept, without prejudice, products and servicesdimensioned in metric units when they are offered at competitiveprices and meet the needs of the Government, and ensure thatacquisition planning considers metric requirements.

  5. PRACTICAL AND MEANINGFUL MEASUREMENTEXPRESSIONS

    1. Whenever possible, federal agencies should use the unitsrecommended in Federal Standard 376 141. Conversion factors, rounding,and other elements of metric system usage not listed in FederalStandard 376, or for units not covered in Federal Standard 376,should be based on the latest editions of the reference documentslisted in Federal Standard 376. 7
    2. Agencies may be able to benefit from the experienceof
      counterpart agencies in other countries where the metric systemhas been recently adopted. For instance, many British and Canadianagencies have already resolved problems similar to those that mayalso arise in the U.S. Government's transition.
    3. Common sense, based on the knowledge and experienceof the agency, should be the most important determinant in choosingpractical and meaningful values, more precisely called "magnitudes,"for the particular purposes involved, Many approaches can be usedfor selecting magnitudes in one measurement system in place of thoseof another. The following "approaches" are offered notas rules or restrictions, but to illustrate factors agencies mayneed to consider: 8
      1. Exact Mathematical Conversion:This process is used to obtain an exact change in measurementunits only -without altering the magnitude. The metric equivalentto an inch-pound magnitude is determined by multiplying by theappropriate conversion factor. The result is then normally roundedin a manner that reflects the precision of the original inch-poundvalue. In exact mathematical conversion, the primary concernis the necessary degree of precision. The new values shouldhave the same degree of precision as that of the value fromwhich the conversion is made. This approach produces what isreferred to as "soft" metric conversion.
      2. Adaptive Conversion: This processchanges a magnitude in one system to a magnitude in anotherthat is reasonably equivalent. Above all, this process shouldresult in conversions to magnitudes that are meaningful andpractical in application.9 Judgments in this process are oftensubjective and may require balancing of competing interests,including magnitudes employed in international standards andpractices in the same or similar areas of application. Thisapproach comes closer to producing what is referred to as "hard"metric conversion.
      3. Size Substitution: In this approachan inch-pound standard size is replaced with an accepted metricstandard size for a particular purpose. Size substitution mightbe used in taxing, selling, or packaging liquids by the liter-instead of by the pint or quart (as for milk), or instead ofby the gallon (as for gasoline), or the choice of square metersinstead of square yards (as for textiles). This is usually doneto conform to international practice, that is, to adopt an internationallyrecognized standard or convention for trade and communication.This approach produces a "hard" metric conversion.
    4. Conversion of the values of quantities should be handledwith careful regard to the implied correspondence between the accuracyof the data and the given number of digits. In all conversions,the number of significant digits retained should be such that accuracyis neither sacrificed nor exaggerated: Net content values on packagelabels are often shown in both inch-pound and metric units. Theconverted values, normally in parentheses, are often rounded toan appropriate degree of precision. The following table illustratesthe above three approaches applied to the same inch-pound values: 10

        Nominal Value: 1lb11 5 lb 10 lb
        Exact
        Mathematical
        Conversion:         		454 g 2.27 kg 4.54 kg
        Adaptive
        Conversion:         		450 g 2.25 kg 4.5 kg
        Size Substitution: 500 g 2.5 kg 5.0 kg

      1. Net content values on package labels are often shownin both inch-pound and metric units. The converted values, normallyin parentheses, are often rounded to an appropriate degree ofprecision. The following table illustrates the above three approachesapplied to the same inch-pound values:10
      2. The speed limits on the nation's interstate highwaynetwork, 55 or 65 miles per hour (mph), is an exact magnitudeimposed by law. A "Exact Mathematical Conversion' of 55mph yields 88.514 kilometers per hour (km/h). "AdaptiveConversion" would yield 88 km/h (or the even moreawkward magnitude of 88.5 km/h). 'Size Substitution' yieldsthe more practical speed limit of 90 km/h, as widelychosen in Canada. Similarly the 65 mph limit might become l00km/h.
      3. Contracts for drilling water wells might requiresampling geologic materials at specific depth intervals, usually10 feet Because these drilling depths are not measured precisely(perhaps they vary by ± 1 ft), it would not seem practicalto convert contract specifications to metric intervals of 3.05meters. A practical and meaningful conversion for this purposemight be 3 meter intervals.
      4. A Federal Communications Commission rule includeda requirement that "two new classes of stations, classesCl and C2, with expected service ranges of 72 kilometers (45miles) and 52 kilometers (32 miles), respectively, will be allowedto operate in Zone II. " Note that instead of an exactmathematical conversion, a practical and meaningful "adaptiveconversion" was chosen that satisfied the agency's purposes.
      5. A recommended regulation on liquid measurement adoptedby the National Conference on Weight and Measures states: "Ona retail device with a designed maximum discharge rate of 25gallons per minute (100 L/min) or greater, the maximum and minimumdischarge rates shall be marked on an exterior surface of thedevice and shall be visible after installation." A practicaland meaningful "adaptive conversion" satisfied theagency's purposes, avoiding a more precise but less practicalmagnitude such as 96 L/min.
      6. The maximum truck body width allowed under the SurfaceTransportation Assistance Act of 1982 is 102 inches. A questionarose as to whether trucks manufactured to the common Europeantruck width of 2.6 meters (102.36 inches) would be allowed onU.S. highways. Common sense prevailed over unnecessary precisionin this ruling; the Federal Highway Administration determinedthe 2.6 meter truck width to be acceptable. .
      7. An EPA regulation specifies: "The samplingpoint for monitoring emissions shall be in the duct at the centroidof the cross section of the smoke stack if the cross sectionalarea is less than 50 ft2 (4.645 m 2) or at a pointno closer to the wall than 3 ft (0.914 m) if the cross sectionalarea is 50 ft² (4.645 m2) or more." Inthis case EPA chose "exact mathematical conversion,"since comparability between new and historical data was desired.
    5. However, a practical and meaningful "adaptive conversion"might have produced: "The sampling point for monitoring emissionsshall be in the duct at the centroid for smoke stacks having a radius<.1.2 m. For stacks >1.2 m the sampling point shall be ata point <92 cm from the stack wall." This would not havenecessitated moving existing fixed measuring devices and would haveallowed newly installed devices to collect samples in the same areaof the smoke plume as devices installed under the inch-pound regulation.
    6. Occasionally, product names may contain nominal dimensions.Such commercial designations are generally not true measurementsand therefore should not be translated arbitrarily to metric units.For example, the "two by four," a nominal descriptionof common lumber, is not actually 2 in. x 4 in. in cross section.Translation to precise metric units could therefore be misleading.
  6. DATA REQUESTS, RECORDKEEPING, AND REPORTS

    It is often necessary to keep historical and current data comparable and consistent in precision, when some of the data are in inch-pound and some are in metric units.

    1. Reports and Questionnaires-Each agency should decide what units will be used in reports itgenerates or requires from the private sector. Whenever the agencyreceives data in one system of units but reports it in another,it is recommended that the agency assume the burden of making theneeded conversion. When metric transition is underway, overlap periodsmay be allowed. Forms can be designed in a variety of ways to providerespondents with options as to which units they use. Dual columns,rows, or pages might be used when choice of units by the respondentis permitted. Alternative versions of the questionnaire (i.e., inch-poundand metric versions) might be provided
    2. Records - During a transitionperiod from one measurement system to another, units from both systemsmust be accommodated. Agencies may encounter a wide variety of problemsduring such time and should plan how they will identify, co-mingle,convert, and ultimately standardize the recording of data. A typicalproblem arises in collecting and storing temperature data. Whereno decimal value has been used for data recorded in degrees Fahrenheit(e.g., 93 °F), reports in degrees Celsius might use incrementsof 0.5 °C to keep approximately the same degree of precision.This is warranted because the Celsius degree is 1.8 times largerthan the Fahrenheit degree. (NOTE: An expression containing onedigit to the right of the decimal point suggests an accuracy ofat least ±0.1. Such precision is not intended in this caseand should be disclaimed if necessary.)
    3. Recordkeeping-- ADP Considerations - Metric conversion, particularly duringtransition, may require computer software modifications. Specialprotocols may be needed to allow for the recording, processing,and display of information in the desired units. Also, the durationfor maintaining dual units and any need to convert or provide conversiontables for historical data should be considered. Issues such asthese should be coordinated by responsible ADP and/or statisticalservices personnel and the agency metric coordinator. The metriccoordinator should be responsible for keeping all parties informedof proposed metric conversions in the agency.
  7. ASSISTANCE

    Assistance in interpreting or implementing these recommendations, or in determining practical and meaningful metric values, is available from the Metric Program Office, U. S. Department of Commerce, National Institute of Standards and Technology, Room A146, Bldg. 411, Gaithersburg, MD 20899, telephone (301) 975-3690. Information on the status of metric conversion for a given industry sector might be obtained from relevant trade associations or the American National Metric Council (ANMC), 4340 East West Highway, Suite 401, Bethesda, MD 20814-2211 and/or the U.S. Metric Association, 10245 Andasol Ave., Northridge, CA 91325-1504. These organizations are involved in planning for the metric transition in the private sector.

Footnotes

1 The 'modernized' metric system is known as the International System of Units or Si (from the French "Le Systeme International d'Unites," which is abbreviated SI), and which is interpreted or modified for use in the United States by the Secretary of Commerce (55 FR 52242, Dec. 20, 1990). (See reference [1].)

2 Metric Conversion Act of 1975 (P.L. 94-168, 89 Stat. 1007; 15 U.S.C. 205 et seq, as amended by the Omnibus Trade Act of 1988, P. L. 100418.)

3 The ICMP is an interagency council chartered by the Secretary of Commerce under authority of EO 12770 (see reference [1]) whose members are senior policy officials representing 39 Federal Agencies that assist in formulating Federal metric policies, in consultation with the private sector.

4 A "measumment-sensitive" law, regulation, recordkeeping requirement or reporting requirement is one whose application or meaning depends substantially on some measured quantity (e.g., mandatory product or performance criteria or standards, such as emission levels, and/or size or weight limitations in shipping.) The mere presence of dimensions or measurement terms does not necessarily make an item "measurement sensitive."

5 The term 'inch-pound' units includes but is not limited to units based upon the inch and the pound commonly used in the United States. Note that "inch-pound" units having the same names in other countries may differ in magnitude.

6 Metric Conversion Act , sec 3(l).

7 Both the American National Standards Institute (ANSI) and the American Society for Testing and Materials (ASTM), publish Metric Practice Standards, ANSI 268 and ASTM E380, respectively.

8 For more technical guidatwe concerning significant digits, precision, accuracy, and tolerances, refer to the appropriate national standards cited in Footnote 7.

9 Often overlooked in conversion is the need to allow for differences in the absolute size of the measurement units involved. For example, 36 inches would normally be converted to 91 centimeters, not 91.44 centimeters, or to 914 millimeters, not 914.4 millimeters. For details see Fed. Std. 376 Section 4.5.

10 An exception to conventional rounding practices may be observed on certain grocery and other consumer items, where the converted quantity is rounded down to avoid overstatement of contents. This practice, which is still recommended by the National Conference on Weights and Measures, calls for dropping all digits of the converted quantity beyond the first three digits where converted metric units are also displayed. The Federal Trade Commission recommends and the Food and Drug Administration requires direct mathematical conversion with rounding procedures such as those set forth in Federal Standard 376.

11 The value "l lb" could conceivably be intended to represent 1, 1.0, 1.00, 1.000, or 1.0000 lb, or even greater accuracy, as might the 5 and 10 lb values. The converted value must be carried to a sufficient number of digits to maintain the accuracy implied or required in the original quantity.

12 40 CFR, Part 57.404(a)(3).

References

  1. Interpretation of the SI and Metric Conversion Policyfor Federal Agencies, NIST SP 814*, which includes:

    •  Metric System of Measurement; Interpretation of the International System of Units for the United States, (55 FR 52242, Dec. 20, 1990); •  Metric Conversion Policy for Federal Agencies, 15 CFR Part 1170; and •  Metric Usage in Federal Government Programs, Executive Order 12770 of July 25, 1991 (56 FR 35801, July 29, 1991).
  2. Guide for the Use of the International System of Units, The ModernizedMetric System, NISTSP 8 1 1 *.
  3. Metrication in Building Design, Production, and Construction-- A Compendium of 10 Papers, NBS SP 530*.
  4. Preferred Metric Units for General Use by the FederalGovernment, Federal Standard 376. The current version, FedStd 376B , dated January 27, 1993 is available from the General ServicesAdministration, Specification Unit (WFSIS), Room 6039, 7th and D Streets,S.W., Washington, DC 20407.
  5. Specifications, Standards, and Other Purchase Descriptions,10(10.02)Federal Acquisition Regulation System (48 CFR), FAC 90-4, April 15,1991.
  6. Use of Metric System Measurement in Federal Product Descriptions,GSA Federal Property Management Regulation (FPMR), Final Rule,41 CFR Part 101-29.
  7. Metric Design Guide, 2nd Edition, GSA Officeof Design and Construction, April 1992.
  8. Use of Metric Measures in FIP Acquisitions, GSAFederal Information Resources Management Regulation (FIRMR), BulletinC-31, January 2, 1992.
  9. Metrication for the Manager, 2nd Edition, John T.Benedict, co-published by: Society of Automotive Engineers, Inc., 400Commonwealth Drive, Warrendale, PA 15096-0001 and American NationalMetric Council, 4340 East West Highway, Suite 401, Bethesda, MD 20814-4411
  10. Metric Editorial Guide, American National MetricCouncil, 4340 East West Highway, Suite 401, Bethesda, MD 20814-4411
  11. Metric Guide for Federal Construction, NationalInstitute of Building Sciences, 1201 Street N.W., Washington, DC 20005
  12. Freeman Training/Education Metric Materials ListU.S. Metric Association, 10245 Andasol Ave., Northridge, CA 91325

    13. *Available from the National Technical InformationService, 5285 Port Royal Rd., Springfield, VA 22161


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