The CSIR-National Physical Laboratory (CSIR-NPL) is an institution and India's National Metrology Institute (NMI), mandated by an Act of Parliament to be the custodian of the nation's measurement standards. Conceptualized in 1943 by the Governing Body of the Council of Scientific and Industrial Research (CSIR), its purpose was to use science and technology for industrial growth and development. The foundation stone was laid by Pandit Jawaharlal Nehru on January 4, 1947, and the main building was formally opened by Sardar Vallabhbhai Patel on January 21, 1950.
CSIR-NPL's core mechanism is to establish, maintain, and continuously upgrade the national primary and secondary standards for physical measurements, ensuring they are traceable to the International System of Units (SI units). It is responsible for realizing the units of measurement under the subordinate legislations of the Weights and Measures Act, 1956 (reissued in 1988 under the 1976 Act). The laboratory maintains six of the seven SI base units, including the metre, kilogramme, and second.
The institution connects directly to the Council of Scientific and Industrial Research (CSIR), under which it was founded. Globally, it is connected to the International Bureau of Weights and Measures (BIPM), having become a member of the General Conference of Weight and Measures (CGPM) in 1957. Recently, the Union Consumer Affairs Ministry notified the Legal Metrology (Indian Standard Time) Rules, 2026, which designate Indian Standard Time (IST) as the sole official time reference, with CSIR-NPL remaining the custodian of India's official time reference, maintaining UTC(NPLI). Furthermore, in 2026, CSIR-NPL inaugurated the National Environmental Standard Laboratory (NESL) to test and recalibrate air pollution monitoring equipment, addressing the need for validation under Indian environmental conditions, which was previously done with foreign certifications.