When Canada Metricfied

As of 2025, only three countries in the world use the Imperial system exclusively: the USA, Liberia, and Myanmar. The United Kingdom, Canada, India, South Africa, and Australia use both Imperial and Metric systems. In Canada, the metric system was adopted around 55 years ago. The Imperial system is still used in certain industries, but metric is preferred.

What is the Imperial Measurement System

The Imperial system is a unit of measurement that was started by Great Britain in 1824. It evolved from thousands of Roman, Celtic, Anglo-Saxon and customary locals in the Middle Ages. Early royal standards established to enforce uniformity took the name Winchester in the 16th century. The name is after the ancient capital of Saxony, Britain, whose 10th-century King Edgar the Peaceful kept a royal bushel measure. Names like pound, foot, and gallon were widely used with varying values of measurement. Customary standards were adjusted throughout history by monarchs like King Henry VII and Queen Elizabeth I to reflect Winchester standards. The Weights and Measures Act of 1824 and 1878 established the usage of the British Imperial System definitions and units.

Customary units of measurement from the United States use the Queen Anne gallon system. A wine gallon of 231 cubic inches is about 17% smaller than the British Imperial System.

What is the Metric Measurement System

The metric system is the standard used throughout most of the world, especially in science. It follows the rule of decimals in increments of tens, hundreds, thousands, etc., to convert from one unit of measurement to the next without complicated conversion factors in between.

For example, one metre is 1000 millimetres.

It was a system introduced after the French Revolution of 1789 that continued discussions of mathematics to replace confusing units of measurement with a system with rational system of multiples of ten. In 1791, the French National Assembly directed the French Academy of Science to address the chaotic system based on a natural physical unit to ensure immutability.

The name metre comes from the Greek, metron, meaning to measure. Names of multiples like hecto, deca, myria and kilo also come from Greek. While milli, centi and devi come from Latin.

Conversion Charts

There are multiple types of uses for the imperial and metric measurement systems. These are basic conversions to common measurements.

Imperial SIzes	Metric Sizes
1 cubic inch	16.4 cubic centimetres
1 grain	0.065 gram
1 ounce	28.35 grams
1 pound	0.45359237 kilogram
1 quarter	12.70 kilograms
1 (imperial) fl. oz.	28.41 ml
1 (US liquid) fl. oz.	29.57 ml
1 inch	25.4 millimetres
1 foot (12 inches)	30.48 centimetres
1 yard (3 feet)	2.7432 metres

In Print

This is referring to page sizes that are very common to see the slight differences in measurement, letter size in Imperial and A4 size in metric. With metric paper, there are three types: A, B, and C. The A series is for general printing. The B series for intermediate sizes in between the A series, for instance, a B4 size is for paper sizes between A3 and A4. The C series for envelopes to match A series paper sizes. This is according to the International Standard Organization (ISO) for paper, ISO 216, that is precut to a commercial size. The C-series for envelopes uses the ISO 269 which regulates the standard sizes of envelopes.

Convert inches to millimetres:

millimetres = inches × 25.4

Convert millimetres to inches:

inches = millimetres ÷ 25.4

This comparison chart of common printing sizes are equalivalent sizes of the former.

Imperial Paper	Imperial Sizes	Metric Paper	Metric Sizes
Quarter Page	4.5 x 5.5 inches	A6 Size	105 x 148 mm
Half Letter	8.5 x 5.5 inches	A5 Size	148 x 210 mm
Letter	8.5 x 11 inches	A4 Size	210 x 297 mm
Legal	8.5 x 14 inches	B4 Size	250 x 353 mm
Tabloid	11 x 17 inches	A3 Size	297 x 420 mm
Double Tabloid (Medium Poster)	18 x 24 inches	A2 Size	420 x 594 mm
Overprint Poster (Large Poster)	24 x 36 inches	A1+ Size	609 x 914 mm
Modern US Movie Poster	27 x 40 inches	—	685.8 x 1016 mm

How did Canada switch to metric?

Think about the biggest scandal in politics was metric conversion. People were pissed and felt like it was forced on them but it was done to make international trade easier.

In Canada, the Imperial system was called the Canadian units of measurement under the Weights and Measures Act. But there were some issues with the system not being universally unified. For example, with cross-border travelling to the U.S., they have a completely different Imperial system called the United States customary units. This can be problematic if you want to fill a car up with a gallon of gas when that could be either a United States gallon, which is 3.77 litres, or an Imperial gallon, which is around 4.77 litres. There are two definitions of a gallon.

The Beginning Canadian Metric Commission

In 1971, Liberal PM Pierre Elliott Trudeau started the Canadian Metric Commission to convert industries into metric from Imperial and recognize the international system of units through the Weights and Measures Act. Canada used the Imperial system due to the historical ties with Britain. But it was inevitable. The whole world used it, especially Britain and France. The conversion was mandatory and difficult. It was called metrication. In the same year, the Consumer Packaging and Labelling Act was there to enforce the usage of metric units on most consumer products.

There were campaigns about the metric system from the government.

The Grocery Store

The most everyday glimpse in metrication was with the food people bought during the conversion. There were items advertised in Imperial units, like steak sold by the pound, when in stores, the packaging printed the product weight in metric units. Items once sold by the pound could be stated as 464 grams as a soft metric conversion, when something was never changed in comparison to 500 grams as a hard metric conversion,n when something was rounded to a nicer number. Most grocery stores and supermarkets use Imperial and metric unit scales for customer usage.

The Milk Bags

The most notable and obvious grocery product that had to change its packaging from a jug to a bag was milk. By 1967, milk was also packaged in thin polyethylene milk bag known as a pillow pouch by the Dupont Company. These are also sometimes called milk bladders but milk bags in Canada. Milk containers were once glass bottles until the metric conversion era in the 1970s that had containers switch from ounces to litres. The milk bags are measured in litres to make to quantity given be exactly the printed amount on the packaging unlike with jugs which were sold in Ontario until the 1990s (which had a returning your empty milk jug containers to the corner store incentive) because hard plastic was easier to manufacture than thin plastic. But by the 2000s, milk is sold in four packs of one-litre milk bags and laminated containers or coated paper containers (such as Tetra Paks) with one-litre of milk.

The Weather

The temperature gauge changed to read both degrees Celsius and Fahrenheit on a thermometer. The weather forecast description, for instance, when the weatherman or meteorologist said it’s 13 degrees Fahrenheit and snowing outside, became -10.5 degrees Celsius. It became harder to comprehend due to the change of units and the comfort people had with the system they were used to.

On April 1st, 1975, the Weather Commission converted to the metric system, despite the timing being April Fool’s Day. But there was a storm near Fredericton, New Brunswick, that was very taxing on the residents in the area, getting their weather details like temperature in metric units.

By 1977, all weather forecasts used metric, but they gave out helpful hints about the weather.

The Road

By 1972, the provinces agreed to change their road signs to metric denominations by 1977. Road signs had a bi-measurement system with the speed signs having metric in large bold numbers (km/h) and the Imperial in smaller letters under the metric (mph). Furthermore, all vehicles had to be sold with the speedometer and odometer in metric conversion.

Gasoline pumps were changed to litres from gallons by 1979. Gas stations had conversion charts to inform consumers filling up their vehicles. They used litres at the pumps, with many drivers confused. 37 parliamentary Progressive Conservatives opposed the changes at the gas station with a “freedom to measure” protest and set up a gas station near Parliament Hill at Carleton Place with the gas in Imperial and metric units. Peterborough MP Bill Domm was one of the loudest voices against the metric system conversion.

Issues with metrification

There were issues with people learning the metric system. Many Tories were against the use of the metric.

But many people were confused by the metric when buying groceries, especially in the deli and dairy sections, which were converted to metric.

It was costly for businesses, and businesses had to change their wording when giving prices. Many said that Imperial made prices sound smaller in description.

But it was more costly with the government. Either the Liberal government stop the metrication, they would have wasted billions of dollars stressing out businesses, but ordering people to convert would have been unconstitutional.

The Gimli Glider

An Air Canada Flight 143, a Boeing 767-200 going from Montreal, Quebec to Edmonton, Alberta, ran out of gas and had to make an emergency landing in July 23, 1983 at a former Royal Canadian Air Force being used as a racetrack in Gimli, Manitoba. Despite both engines failing, Captain Bob Pearson and First Officer Maurice Quintal landed the plane after gliding for 17 minutes before bring the aircraft down. It was due to a miscalculation of the metric system for the needed fuel for the flight. They only had half of the fuel needed. Everyone was able to escape with no serious injuries. Both pilots received the Fédération Aéronautique Internationale Diploma for Outstanding Airmanship due to the unusual landing after being reprimanded by Air Canada, according to Damn Interesting article about the Gimli Glider “for not observing the Minimum Equipment List (MEL) and grounded the aircraft since it lacked functioning fuel gauges.” The plane was retired in 2008 with the two pilots and three out of six attendants attending the ceremony.

The End of the Metric Commission

When Conservative PM Brian Mulroney entered office in 1985, he ended the Metric Commission and made metrification voluntary. Metric was still mandatory in gas, diesel and home furnishings. Small businesses were exempt from installing small scales in metric units.

People in Canada are pretty integrated with metric for certain things like speed limits, grocery items and gas, and Imperial for other things like print, a person’s weight and height. The Imperial system still has some influence in Canada because of trade, mainly with the United States, which still uses the Imperial system in everything. They came close to converting to implementing bi-measurement highway road signs in Imperial and metric in the late 1970s.

This is a 45-minute informational film by the government of Ontario to explain the metric system to the people. It’s actually interesting if you want to watch a film about mathematical units of measurement.