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 on 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. The Indian model was extremely successful and served later as a model for metrication in various African and Asian countries.
Before metrication, the government of India followed the Indian Weights and Measures Act passed in 1870 which used the British imperial system. However, many other indigenous systems were in use in other parts of the country and this was a constant problem with government officials and the public at large.
P. N. Seth was the founder and secretary of the Indian Decimal Society, whose aim it was to push for the introduction of the metric system in India. P. N. Seth was assisted by others in the society, such as professors Dr H. L. Roy, Dr S. K. Mitra, and P. C. Mahalanobis, and other leading Indian scientists. Since 1930, they advocated for discarding the old chaotic system by writing in newspapers, journals, participating in debates and distributing literature.
During the post-WWII interim government, there were attempts to introduce some standardisation in weights and measures but the conservative section of the ruling party never allowed it to be passed. Then, outstanding scientific personalities and public figures were mobilised by the Indian Decimal Society. P. N. Seth put forward a scheme for metrication of currency on 17 January 1944, which was finally adopted in the Indian Parliament in 1955.
Common usage today
Today all official measurements are made in the metric system. However, in common usage some older Indians may still refer to imperial units.
Exception to Metrication
- The heights of mountains are still recorded in feet.
- The Indian numbering system of crores and lakhs are used.
- Tyre rim diameters are still measured in inches, as used worldwide.
- Road widths are popularly measured in feet but official documents use metres.
- Body temperature is still sometimes measured in degrees Fahrenheit.
- Industries like the construction and the real estate industry still use both the metric and the imperial system, though it is more common for sizes of homes to be given in square feet and land in acres.
- Bulk cotton is sold by the candy (0.35 imperial tons, or 355.62 kg) or the bale (170 kg).
- Fruits are sold by kilograms or dozens.
- The Delhi Jal Board uses MGD (million gallons daily) for water supply measurements.
- The motor industry still uses brake horsepower (bhp) for engine power.
- The Indian Boiler Act mentions five gallons as 22.75 litres.
- Tyre tubes and carbonated beverages are filled on the psi scale.
- Clothing sizes are given in an even numbers of inches.
- Shoes sizes increment by one-third of an inch.
- Football pitches are measured along the ground in yards and height in feet.
- Ladders are sold per foot.
- Display sizes for screens on television sets and computer monitors and measured diagonally in inches.
- Like in most countries, aviation (altitude and flight level) is measured in feet.
- Acharya, Anil Kumar. History of Decimalisation Movement in India, Auto-Print & Publicity House, 1958.