Although there was debate in Australia's first parliament after federation to consider adopting the metric system, metric units first became legal for use in Australia in 1947 when Australia signed the
Metre Convention (). However, imperial weights and measures were most commonly used until the federal government began the metric changeover in the 1970s. SI units were subsequently adopted as the basis for Australia's measurement standards, thereby becoming Australia's legal units of measurement. In 1968, a
select committee of the Australian senate chaired by
Keith Laught examined metric weights and measures and came to the unanimous conclusion that it was both practical and desirable for Australia to change to the metric system. Some of their considerations included the "inherent advantages of the metric system" that meant that weighing and measuring was facilitated, "often with substantial increases in efficiency". Educationally, the reform would "simplify and unify the teaching of mathematics and science, reduce errors, save teaching time and give a better understanding of basic physical principles". In 1968, more than 75% of Australia's exports went to metric countries, and at that time it was noted that all countries (except the
United States) were using metric units or were converting to the metric system. It was also noted that, because of Australia's large migrant program, more than 10 percent of people aged 16 or older had used the metric system before coming to Australia. They also noted that school pupils were widely familiar with the metric system because it had been taught in the schools for many years. By 1968, metrication was already well underway in Australian industry. The pharmaceutical industry had metricated in 1965, and much of the chemical and electronics industries worked in metric units, as there were no imperial units for the latter. One of the country's major automobile manufacturers had already declared its intention to metricate before the government announced its decision to change to the metric system. "The change itself provided a unique opportunity to rationalise and modernise industrial practices and bring Australia's technical standard specifications into accord with those adopted internationally". • 1973 – All primary schools were teaching the metric system alone: many had been teaching both imperial and metric for some years. All secondary schools were now using the metric system. • 1974 – Large scale conversion across industries, including packaged
grains,
dairy products,
eggs,
building,
timber,
paper,
printing,
meteorological services,
postal services,
communications,
road transport,
travel,
textiles,
gas,
electricity,
surveying,
sport,
water supply,
mining,
metallurgy,
chemicals,
petroleum, and
automotive services. Most
beverages, aside from spirits, were also converted to metric units by the end of the year. The conversion of road signs took place in July, aided by a publicity campaign to prepare the public. • 1976 – The building and construction industry completed its change to metric measurements (within two years) by January. • 1977 – All packaged goods were labelled in metric units, and the
air transport,
food,
energy,
machine tool,
electronic,
electrical engineering, and appliance
manufacturing industries converted to metric. • 1987 – The property industry, the last major industry holdout, converted to metric. • 1988 – With Western Australia fully implementing the change, metrication was completed nationwide, and the metric system became the only system of legal measurements in Australia.
Metric Conversion Board Opposition to metrication was not widespread.
Metrication of horse racing An early change was the metrication of
horse racing. This was facilitated because the
furlong () is close to . Therefore, the
Melbourne Cup was changed from to , a reduction of about or about 0.6%. The first metric Melbourne Cup was raced in November 1972.
Metrication of weather reporting and forecasts When the Australian
Bureau of Meteorology was enlisted to introduce the metric system for weather reporting and forecasts, its public relations officer, Godfrey Wiseman, coined a series of
jingles to educate the public, using the terms
frosty fives,
tingling tens,
temperate twenties,
thirsty thirties and
fiery forties to describe human sensation to temperatures in degrees Celsius. This was very successful because the public soon became aware of the significance of the descriptions. At the culmination of this campaign, weather reports and forecasts in both
Fahrenheit and
Celsius were provided for only one month. After that, from 1 September 1972, only Celsius measurements were given for temperature. Similarly,
wind speed was reported only in kilometres per hour (km/h) from 1 April 1973, and rainfall was reported in
millimetres with river depths, snow depths and waves reported in metres from 1 January 1974.
Metrication of the road signs An important and very visible sign of metric conversion in Australia was the change in
road signs and the accompanying traffic regulations; "M-day" for this change was 1 July 1974. Because of careful planning, almost every road sign in Australia was converted within a month. This was achieved by installing covered metric signs alongside the imperial signs before the change, and then removing the imperial signs and uncovering the metric signs during the month of conversion. While road signs could not all be changed at the same time, there was little chance of confusion as to what any
speed limit sign meant during this short change-over period. This was because the previous mph signs had black-on-white rectangular signage, in the same style as current US speed limit signs, whilst the km/h signs that replaced them had the speed limit number inside a red circle, as is done in Europe. Road distance signs were also converted during this period. To avoid confusion as to whether the distance indicated was in miles or kilometres, new major distance signs had affixed to them a temporary yellow plate showing the symbol
km. This was distributed through post offices, police stations, and motor registry offices. Kevin Wilkes wrote:
Building and construction showing millimetres The building industry was the first major industry group in Australia to complete its transition to the metric system. This was achieved within two years by January 1976 for all new buildings other than those for which design had commenced well before metrication began. The resulting savings for builders and their sub-contractors have been estimated at 10% of gross turnover. In this, the industry was grateful to Standards Australia for the early publication of the standard AS 1155–1974, "Metric Units for Use in the Construction Industry", which specified the use of millimetres as the small unit for the metrication upgrade. In adopting the millimetre as the "small" unit of length for metrication (instead of the centimetre), the Metric Conversion Board relied heavily on experience in the United Kingdom and with the International Organisation for Standardisation, where this decision had already been made. The logic of using the millimetre in this context was that the metric system was designed so that there would be a multiple or submultiple for every use. Decimal fractions would not have to be used. Since the tolerances on building components and building practice would rarely be less than , the millimetre became the sub-unit most appropriate to this industry.
Electrical wiring converted from imperial measurements such as , , , or to metric , or wire sizes. ==Exceptions==