Metric Conversion | The Canadian Encyclopedia


Metric Conversion

Metric conversion was the process of making metric units — such as metre, kilogram and degree Celsius — the common units of measurement in Canada, leaving the British imperial system (with units such as yard, gallon and pound) behind. The process was fraught with political interference and public resistance, and took place incrementally between 1970 and the early 1980s. Despite the shift, many Canadians still express certain measurements in imperial units, such as height (feet and inches).


Although the metric system was first legalized in Canada by Prime Minister John A. Macdonald in 1871, the British imperial system of units (based on yards, pounds, gallons, etc.) continued to predominate. In the 1960s, with rapidly advancing technology and expanding worldwide trade, the need for an international measurement system became increasingly apparent. In addition, the size of measurements such as the gallon differed between the United States and Canada, despite both countries using the imperial system. Beginning with a White Paper in 1970, Canada gradually began to convert from an imperial to a metric system of measurements.

1970 White Paper on Metric Conversion

In the years leading up to 1970, a number of Canadian associations representing diverse interests, including consumers, educators and professionals, lobbied the federal government to switch from the imperial to metric measurement system.

They cited many benefits including export trade and international standardization. In addition, lobbyists noted the simplicity of a metric system because of its decimal nature and the absence of a multiplicity of units with conversion factors. The universality of metric symbols (regardless of language) and the convenience of having a single unit for a physical quantity would make communications easier.

In January 1970 the “White Paper on Metric Conversion in Canada” set out Canadian government policy. It stated that a single, coherent measurement system based on metric units should be used for all measurement purposes, including legislation. In line with this policy, the Weights and Measures Act was amended by Parliament in 1971 to recognize the international system of units (SI), the latest evolution of the metric system, for use in Canada. Also in 1971, Parliament passed the Consumer Packaging and Labelling Act, requiring that metric units be shown on labels of most consumer products.


To implement metric conversion the government established a preparatory commission in 1971, later called Metric Commission Canada. The commission's role was to ensure a planned and coordinated conversion in all sectors of the Canadian economy and to disseminate information on metric conversion. Beginning in 1973, the commission organized over 100 sector committees, with members from national associations and major organizations representing business, industry, consumers, labour, health, education and government. Each sector committee was responsible for preparing a sector conversion plan and monitoring its implementation. The commission as a whole approved sector conversion plans developed through consensus.

Establishing the Metric System

The process of replacing imperial units with SI units in all kinds of documents, measuring devices, manufacturing processes, products and packages involved a countless variety of tasks. The technical basis for the change to SI units was established by two sets of standards: the international system of units (SI) and the Canadian Metric Practice Guide, first published in 1973 by the Canadian Standards Association and approved by the Standards Council of Canada.

After choosing appropriate SI units, practical approaches to implementation were debated by sector committees, with each sector determining policies and strategies to suit its interests. Soft conversion (arithmetical conversion of pre-existing measurement values) versus hard conversion (round, rational values in metric units, possibly requiring physical change in product size) was a major issue. The use of both imperial and metric measurements was another area of controversy. Dependence on the United States for many parts and products was a constraint for many sectors. The dedicated efforts of Canadian industry allowed conversion to proceed with few major problems, although it took between two and five years longer than planned.

Education and public-awareness programs were important considerations to ensure public understanding and acceptance of the change to metric units. With the cooperation of all provinces, schools prepared to teach mainly the metric system. A series of metric conversion events exposed the public to simple metric units in everyday life; extensive information campaigns accompanied each change. The first such event was the announcement of temperature in degrees Celsius in weather forecasts beginning 1 April 1975. From September 1975, rainfall and snowfall were quoted in millimetres and centimetres, respectively. The next significant change (September 1977) was the introduction of road signs showing distances in kilometres and speed limits in kilometres per hour. Concurrent with this change, cars with speedometers and odometers graduated in metric units were produced.

In January 1979, service stations started pricing and dispensing gasoline and diesel fuel in litres. In December 1980 (the cut-off date for using imperial units), fabrics and home furnishings were required to be advertised and sold only by the metre and centimetre.

Conversion of weighing scales in retail food stores created political controversies. After three pilot areas (Kamloops, Peterborough and Sherbrooke) completed scale conversion in the summer of 1979, national conversion was postponed by the minority Conservative government headed by Joe Clark, but was resumed in January 1982 under Pierre Trudeau’s Liberal government. Cut-off dates were established for different areas, extending up to December 1983. After that, store-weighed food items could be priced and advertised only by kilogram or 100-gram quantities and sold only in metric units. Conversion involved some 35,000 retail food stores across Canada. Metric units steadily became normal for most products and services. However, certain areas of business did hold out against conversion, such as real estate.

Legislation of Metric Conversion

Metric conversion proceeded voluntarily in many sectors, but federal and provincial legislative action was required in some. Regulations on the use of metric units for weights and measures in retail trade were established and enforced by the government for the protection of consumers and retailers against unfair practices and confusion in comparing products.

Political and Public Resistance

The government did not escape criticism for imposing mandatory use of metric units to the exclusion of old units. Opponents of metric conversion pointed to the costs at a time of inflation and economic weakness, the danger of being out of step with the United States and the invasion of a foreign language of measurements upon a Canadian heritage bound to imperial measurements. Some challenged metrication through the courts.

Included among the voices of resistance was an editorial in the Toronto Sun opposing metrication. The newspaper also organized a petition with the names of tens of thousands of Canadians opposed to converting to metric.

Much of the debate was partisan, with the Liberal government supporting mandatory conversion and many Conservative MPs opposing it. In 1982, Neil Fraser, a tax auditor in the Department of National Revenue, was fired from the Liberal administration for publicly opposing metric conversion.

Adding fuel to the argument against metrication was the “Gimli Glider” incident: in 1983, Air Canada Flight 143 from Montreal to Edmonton had to make an emergency landing near Gimli, Manitoba, because it ran out of fuel. The shortage was caused by a miscalculation of the metric amount of fuel needed for the flight, giving the plane only half the fuel it needed.

Brian Mulroney's Conservative government reaffirmed the commitment to metric but revoked the required use of metric alone in some cases, including gasoline, diesel fuels and home furnishings. In 1985, some small businesses were exempted from the requirement to install metric scales.

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