Metrication in India

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Metrication, or the conversion to a measurement system based on the International System of Units (SI), occurred in India in stages between 1955 and 1962. The metric system in weights and measures was adopted by the Indian Parliament in December 1956 with the Standards of Weights and Measures Act, which took effect beginning 1 October 1958. The Indian Coinage Act was passed in 1955 by the Government of India to introduce decimal coinage in the country. The new system of coins became legal tender in April 1957, where the rupee consists of 100 paise. For the next five years, both the old and new systems were legal. In April 1962, all other systems were banned. This process of metrication is called "big-bang" route, which is to simultaneously outlaw the use of pre-metric measurement, metricate, reissue all government publications and laws, and change the education systems to metric.

India's conversion was quicker than that of many other countries, including its coloniser, the United Kingdom. This was helped by low popular literacy and the fact that there was previously no nationwide standard measurement system—British imperial units were used by the upper class, while various regional systems were used by the poor^{[citation needed]}. The Indian model was extremely successful and served later as a model for metrication in various African and Asian countries.

The National Physical Laboratory of India, located in New Delhi, is designated the maintainer of SI units in India. It also calibrates the national standards of weights and measures.