The question in the title of the article asks which countries use the metric system — more accurately called the International System of Units — but it would be much easier to list which countries don't use it. There are only three: Myanmar (or Burma), Liberia and the United States.
Only three countries – the U.S., Liberia and Myanmar – still (mostly or officially) stick to the imperial system, which uses distances, weight, height or area measurements that can ultimately be traced back to body parts or everyday items.
Only three countries have not yet taken on the metric system as their official gauge of measurements. The United States, Liberia and Myanmar, while the system isn't completely foreign being used for certain endeavors, the three refuse to make the system the law of the land.
So why hasn't it changed? The biggest reasons the U.S. hasn't adopted the metric system are simply time and money. When the Industrial Revolution began in the country, expensive manufacturing plants became a main source of American jobs and consumer products.
Countries that do not use the metric system
In truth, every country in the world uses the metric system to some extent. However, a few countries, including not only the United States, Liberia, and Myanmar, but also Canada, and the United Kingdom, have not yet converted 100% to metric.
With every other country in the world adopting the metric system, you have to wonder why Liberia, Myanmar and the United States are holdouts.
– Easy! It's not a secret that all measurements in Russia are done in the metric system. Do you find all those meters, centimeters, liters and kilograms confusing? They are actually not that terrible as they look like.
In 1947 Australia signed the Metre Convention, making metric units legal for use in Australia. In 1970 the Metric Conversion Act was passed, allowing for the metric system to become the sole system of measurement.
The basis of the argument is that while the metric system of units is based on scientific constants, the imperial system is based on the size of everyday items. From Real Clear Science: While the metric units' association with physical constants makes them accurate, it makes them less practical for common use.
The French are widely credited with originating the metric system of measurement. The French government officially adopted the system in 1795, but only after more than a century of sometimes contentious bickering over its value and suspicion surrounding the intent of metric proponents.
Only three countries in the world don't use the metric system: the United States, Liberia, and Myanmar.
While not mandating metric use in the private sector, the federal government has sought to serve as a catalyst in the metric conversion of the country's trade, industry, and commerce. Exceptions were made for the highway and construction industries.
Metric is simply a better system of units than imperial
In other words, it fits together very well and calculations are easy because it is decimal. This is a big advantage for use in the home, education, industry and science.
Australia uses the metric system for most quantities: The modern form of the metric system is the International System of Units (SI). Australia also uses some non-SI legal units of measurement, which are listed in Schedules 1 and 2 of the National Measurement Regulations.
For example, some customers ask for one pound (ein Pfund) of something when they want 500 grams. The metric system became compulsory on 1 January 1872, in Germany and on 1 January 1876, in Austria.
Adopting the metric system was discussed in Parliament as early as 1818 and some industries and government agencies had metricated, or were in the process of metricating by the mid-1960s. A formal government policy to support metrication was agreed by 1965.
Imperial units, also called British Imperial System, units of measurement of the British Imperial System, the traditional system of weights and measures used officially in Great Britain from 1824 until the adoption of the metric system beginning in 1965.
Imperial units such as feet, pints, ounces and miles are used alongside metric units like metres, millilitres and kilometres. In the UK we use metric for money (pence) and imperial for large distances (miles).
In other words, the French introduced not only national standards, but a system of standards. It survives today as the metric system.
New Zealand started metrication in 1969 with the establishment of the Metric Advisory Board (MAB) and completed metrication on 14 December 1976. Until the 1970s, New Zealand traditionally used the imperial system for measurement, which it had inherited from the United Kingdom.
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.
In 1972, Australians had to learn a new way to describe the weather, when the Bureau of Meteorology changed to the metric system. This ABC News report explains the change in terms such as 'fahrenheit', to degrees 'celsius'.
On August 7, 2018, Ukraine gained full membership in the Metric Convention and became one of the 60 member states. By this time Ukraine has been in the status of associate member for 16 years.
As such, there are only three countries in the world that do not use the metric system; the U.S, Liberia, and Myanmar.