In 1930, the
British Standards Institution adopted an inch of exactly 25.4 mm. The
American Standards Association followed suit in 1933. By 1935, industry in 16 countries had adopted the "industrial inch" as it came to be known,
[30][31] effectively endorsing Johannson's pragmatic choice of conversion ratio.
[27]
In 1946, the Commonwealth Science Congress recommended a yard of exactly 0.9144 metres for adoption throughout the British Commonwealth. This was adopted by Canada in 1951;
[32][33] the United States on 1 July 1959;
[34][35][36] Australia in 1961,
[37] effective 1 January 1964;
[38] and the United Kingdom in 1963,
[39] effective on 1 January 1964.
[40] The new standards gave an inch of exactly 25.4 mm, 1.7 millionths of an inch longer than the old imperial inch and 2 millionths of an inch shorter than the old US inch.
[41][42]
