Rules 22 explained: this guide covers what it means, who it applies to, the step-by-step process, documents required, fees, due dates and penalties in India — so you can stay compliant with confidence and avoid costly mistakes.
The last two chapters of the National Standards Rules explain who holds the country's primary standards, how they are kept and compared with the world's, and how the chain of reference, secondary and working standards below them is made, placed and re-verified. Rules 22 to 25 deal with the national prototypes and the National Physical Laboratory; rules 26 to 32 with the three levels of standards; rule 33 repeals the 1988 rules.
These rules are as amended up to the Legal Metrology (National Standards) (Amendment) Rules, 2019, which substituted rules 4 to 10 only; later amendments should be checked on the Department of Consumer Affairs website. If you run a calibration laboratory or maintain standard weights and need to plan your verification cycle, a legal consultation is a good first step.
The National Physical Laboratory (NPL), New Delhi, is responsible for realising, keeping and updating the national standards, and national prototypes are deposited with it. Its standards are compared with international ones at intervals of not more than ten years, and their values are published at least once in every five years. A reference standard is verified every three years (five for length measures), a secondary standard every two years and a working standard every year.
Chapter III: national standards (rules 22 to 25)
Rule 22: national prototypes
- Rule 22(1). To derive the value of the kilogram, the Central Government has a national prototype of the kilogram prepared, its accuracy certified by the International Bureau of Weights and Measures as equivalent to the international prototype of the kilogram, and deposits it in the custody of the National Physical Laboratory, New Delhi.
- Rule 22(2). Likewise for the metre: a national prototype of the metre is prepared, certified by the International Bureau and deposited with the National Physical Laboratory.
The 2019 amendment redefined the kilogram and the metre through constants (see our article on rules 1 to 11), but did not touch rules 22(1), 24(4) and 25. These rules are stated here as printed, and still speak of a "national prototype of the kilogram".
Rule 23: custody and maintenance
On commencement, the work of realisation, establishment, custody, maintenance, determination, reproduction and updating of the national standards is the responsibility of the National Physical Laboratory (23(1)). The Central Government may call for reports from, or give directions to, the Laboratory on any of those matters (23(2)).
Rule 24: realisation based on SI units
- The Laboratory realises and establishes the national standards on the basis of recommendations of the General Conference on Weights and Measures or the International Organisation of Legal Metrology, as the case may be (24(1)).
- The standards so realised and established are self-consistent (24(2)).
- For base units other than mass, the Laboratory prepares the objects or equipment, or reproduces phenomena, and determines the value of the national standards as recommended by the General Conference, inter-comparing them with the international standards (24(3)).
- For the kilogram, the Laboratory arranges the periodical determination of the value of the national prototype of the kilogram, and that value is the national standard of mass (24(4)).
- For derived and supplementary units, the Laboratory prepares standards, objects or equipment and periodically determines their value and accuracy against the base-unit standards (24(5)).
Rule 25: custody and maintenance of prototype standards
- The national prototype of the kilogram and other standards, equipment and objects stay in the custody of the National Physical Laboratory, New Delhi (25(1)).
- They are maintained and realised periodically per instructions of the General Conference, the International Organisation of Legal Metrology or any organisation constituted by either (25(2)); if the International Organisation has issued none, a Consultative Committee constituted may compile instructions (25(3)).
- The Laboratory arranges, where necessary, to have them realised in accordance with the General Conference's recommendations and calibrated or inter-compared with international standards at periodical intervals of not more than ten years (25(4)).
- Their value is the one determined or assigned by the Laboratory, and the Laboratory publishes the values periodically, in any case at least once in every five years (25(5)).
- The value so determined is deemed to represent the highest obtainable accuracy of such value in the country (25(6)).
Chapter IV: reference, secondary and working standards (rules 26 to 32)
Definitions (rules 26 to 28)
| Standard | Meaning in the rules |
|---|---|
| Reference standard | A set of standard weight or measure made by or on behalf of the Central Government for verification of any secondary standard |
| Secondary standard | A set of standard weight or measure made by or on behalf of the Central or a State Government for verification of any working standard |
| Working standard | A set of standard weight or measure made by or on behalf of the Central or a State Government for verification of any standard weight or measure, other than the national prototype, reference standard or secondary standards |
For how the General Rules use the same three terms, see our post on rules 3 to 6 of the General Rules; the Act's sections are in sections 9 and 10.
Rule 29: fabrication by the Mint
Unless the Central Government specifies otherwise, all reference, secondary and working standards of mass and length, and secondary and working standards of capacity, are fabricated by the Metrological Wing of the Government of India Mint in Mumbai.
Rule 30: where standards are kept
- The Central Government establishes, at places it thinks fit, Reference Standard Laboratories to maintain the reference, secondary and working standards it needs for the Act (30(1)).
- The Indian Institute of Legal Metrology, or another laboratory the Central Government specifies, may also maintain such standards, functioning as a metrological laboratory of the level of a Reference Standard Laboratory (30(2)). For the Institute see our article on its rules.
- The Government of India Mint at Mumbai may maintain standards needed for the work in rule 29 (30(3)).
Rule 31: verification intervals
| Standard | Verified by | Against | Interval as printed |
|---|---|---|---|
| Reference standard | National Physical Laboratory | The National Standards | Not exceeding three years; for length measures, not exceeding five years |
| Secondary standard | The Reference Standard Laboratory | The appropriate reference standard | Not exceeding two years |
| Working standard | Any laboratory where secondary standards are maintained | The appropriate secondary standard | Not exceeding one year |
Rule 32: maintenance
Every reference, secondary and working standard, wherever kept, is maintained as far as practicable in accordance with the guidelines issued by the National Physical Laboratory from time to time.
Rule 33: repeal and savings
The Standards of Weights and Measures (National Standards) Rules, 1988 are repealed, without affecting previous operations, rights, liabilities, penalties, investigations or proceedings under them. Things done under the old rules, such as approvals, exemptions, fees collected and registrations of manufacturers, dealers, importers and repairers, continue as if done under the corresponding provisions of the 2011 rules. Pending applications, court proceedings and appeals under the old rules carry over.
The chain at a glance
- National prototypes and national standards: custody and realisation at the National Physical Laboratory, compared internationally at intervals of not more than ten years, published at least once in every five years.
- Reference standards: verified and certified by the Laboratory, every three years (five for length).
- Secondary standards: verified against reference standards, every two years.
- Working standards: verified against secondary standards, every year.
A practical example
A State legal metrology laboratory keeps a set of working standard masses made on behalf of the State Government. Under rule 31(3) the set must be verified against the appropriate secondary standard at an interval not exceeding one year, by a laboratory where secondary standards are maintained. The laboratory's staff set a reminder at eleven months, so that the certificate does not lapse. The secondary standard in turn has a two-year cycle with the Reference Standard Laboratory.
Common lapses
- Missing the one-year interval for working standards or the two-year interval for secondary standards.
- Treating the five-year interval for length measures as applying to mass or capacity.
- Verifying a working standard against an unverified secondary standard.
- Not following the National Physical Laboratory's maintenance guidelines under rule 32.
Need help with standards and calibration compliance?
If you maintain standard weights or measures and want to make sure your verification cycle matches the rules, our team can help you plan it. Start with a legal consultation.
Key takeaways
- The National Physical Laboratory, New Delhi, holds the national prototypes and is responsible for national standards.
- National standards are compared internationally at intervals of not more than ten years and their values published at least once in every five years.
- Reference standards: every three years (five for length measures); secondary: every two years; working: every year.
- The Government of India Mint, Mumbai, fabricates reference, secondary and working standards of mass and length, and secondary and working standards of capacity, unless otherwise specified.
- Rules 22(1), 24(4) and 25 still speak of a national prototype of the kilogram; the 2019 amendment did not change them.
Read next
- Rules 1–11: definitions and the seven base units after the 2019 amendment
- Rules 12–21: derived, permitted, special and discontinued units and the ten Schedules
- Rules 3, 4, 5 and 6 of the General Rules: reference, secondary and working standards
Disclaimer: Based on the Legal Metrology (Approval of Models) Rules, 2011 (as amended in 2019), the Legal Metrology (Government Approved Test Centre) Rules, 2013 (as amended up to 17 June 2026), the Legal Metrology (National Standards) Rules, 2011 (as amended in 2019), the Legal Metrology (Numeration) Rules, 2011 and the Indian Institute of Legal Metrology Rules, 2011, as published in the Gazette of India and consulted on 4 October 2026. Later amendments, current fees and the Legal Metrology Act, 2009 provisions referred to should be checked on the Department of Consumer Affairs website. This article is general information, not legal advice; check the official text before acting.