Units of measurement are fundamental to how humans engage with the world. They allow us to understand everything that surrounds us through the same eyes and to have a common system by which we divide and make sense of the world.

Although there were several precursors, the metric system has become the global standard for measurements, and the meter is the standard unit of measurement within the metric system. When measuring longer distances, the kilometer is the metric used, as a kilometer is equivalent to 1,000 meters.

The meter was created in the context of the French revolution at the end of the 18th century, and the kilometer came shortly after. As one system usurped another, the new order saw it fit to rewrite the old rules and develop a measurement system based on the Earth's size that would be universal and standardised.

We are going to explore everything there is to know about the kilometer, what it is, its equivalences, where it is used, and why it came about.

A kilometer, or kilometre, is a unit of length in the International Standard of Units, equivalent to 1,000 meters and roughly 0.621 miles. It was first developed in France after the French revolution and has since become the standard distance measure for roadsigns in most countries worldwide.

Although the UK has adopted elements of the metric system since joining the EU in 1973, all roadsigns are still written in miles over kilometers. This means that the UK is one of only a handful of countries that has yet to fully transition to the metric system.

So let's jump in and find out exactly how long a kilometer really is.

Under the metric system, the distance of a kilometer is directly related to the length of a meter.

A kilometer is equivalent to:

  • 1000 meters
  • 3281 feet
  • 1094 yards
  • 0.621 miles is about one kilometer, but the exact number is longer and more precise.

In the 18th century, the newly formed French Republic decreed that the meter was to be the sole length measurement system.

However, while it may seem simple to us, defining a meter for the people who invented the concept was a complicated process.

1 meter was initially defined as 1/10 millionth of the distance from either the North or South poles to the Equator. That way, the measurement would be international and universal.

A few years later, the 'true' meter measurement was redefined in terms of a meter bar used as the official prototype meter. Throughout the 20th century, the definition of meter was adjusted several times, with the most recent measure being defined as the distance light travels in a vacuum in 1/299792458th of a second.

Every definition has moved closer to a more precise and universal metric.

So, the truthful answer to the question, 'how far is a kilometer?' is to say that the distance has changed over time as the length of the meter has been adjusted. But our current definition is:

  • (the length of the path travelled by light in a vacuum in 1/299792458th of a second) x 1,000

The meter was invented in 1793, and the first reference to the kilometer came in 1799. Both units were developed within the context of the French revolution and the new French Republic.

The French revolution (1789-1799) saw the deaths of over 40,000 people, the execution and deposition of the French monarchy, and the establishment of the French Republic. The new leaders of France saw the radical shift in power as an opportune moment to rid the country of its archaic systems of weights, measurements, and time.

While the new calendrical and time systems didn't last long, the outdated weights and measurement systems needed revision. The new rulers (no pun intended) wanted to create a standardised system that could be used worldwide, and in 1791 the French Academy of Sciences set up a commission specifically for such a purpose.

The commission concluded that the standard unit of length should be based on the size of the Earth so no country was discriminated against and everywhere would be the same.

Because of the spread of colonialism and the European empires, there was a greater need for universal systems that could transport and translate to other cultures and communities. So the metric system was fairly hastily adopted by much of Europe soon after it was initially conceived.

The metric system is a system of measurement that succeeded the decimalised system. It is built on the base units of 1, 10, 100, and 1000.

The different units of measurement link with one another. For example, one liter of water weighs one kilogram because a gram is defined as one cubic centimeter of water. Combined with the simple base units, this makes it simple to convert kilometers and all the other metric units.

The metric system uses the meter as the standard unit of measurement. As we have seen, the exact measurement of a meter has evolved over time, but the relationship between the different units has remained the same. Therefore, the system remains standardised because when one unit changes, the others do too.

The etymology of 'meter' trace back to the Greek 'metreo,' which means to measure, count, or compare, and 'metron,' meaning a measure.

'Kilo' means a thousand in French. It is also derived from Greek, with the Greek word 'khilioi' meaning a thousand.

Before the kilometer, there were multiple units of measurement that were imprecise and non-universalised. The most common distance measurements were miles and yards.

Miles and yards had been used for millennia. However, there was no worldwide standard definition, so it was very hard, if not impossible, to convert measurements from one country or region into other units from different places.

For example, a Roman mile was a length equal to the distance of a thousand paces, with every other step counted as one pace. While an English mile was so imprecise that its measurements seemed to have varied depending on what part of England you were in.

There were attempts to create a universal standardised system before the metric system, but none were entirely successful.

After its inception, the metric system quickly spread throughout the French empire and was adopted by most Europe countries by the end of the 19th century. The spread of the metric system is known as 'metrication.'

In 1952, the International System of Measurements was introduced as a standardised, universal measurement system. Since then, the metric system and the kilometer have been adopted by most countries in the world.

However, there are still countries that use miles for road signs. Countries that have yet to move to kilometers and still use miles include:

  • Antigua and Barbuda
  • Bahamas
  • Belize
  • Dominica
  • Grenada
  • Liberia
  • Marshall Islands
  • Micronesia
  • Myanmar
  • Palau
  • Saint Kitts and Nevis
  • Saint Lucia
  • Saint Vincent and the Grenadines
  • Samoa
  • United Kingdom
  • United States

In addition to not using kilometers, there are seven countries that have not adopted any components of the metric system. They are:

  • Liberia
  • Marshall Islands
  • Micronesia
  • Myanmar
  • Palau
  • Samoa
  • United States.

The UK is in an odd position regarding metrication. While the US still uses the US Customary Units - pounds, inches, ounces, etc. - and most other countries have fully incorporated the metric system, the UK is somewhere between the two.

It is not uncommon for older Brits to still use imperial units and talk about temperature in Fahrenheit, weigh things in stones and pounds, and measure length in feet and inches. However, younger generations are more likely to use metric measurements such as kilograms and centimeters, though they may use both.

The UK was initially reluctant to adopt the metric system as it was first popularised in France during the Napoleonic era, during which the English were at war with the French. Since joining the EU in 1973, the UK gradually switched to using some metric measures to comply with the rest of the union.

But this hasn't happened across the board. For example, milk and beer are often measured in pints, and the roadsigns in the UK are still written in miles.

A kilometer is a metric unit that was first created in the late 18th century in post-revolution France and is equivalent to 1,000 meters or (roughly) 0.621 miles. It has since become an international standard unit of measurement that is used worldwide for measuring long distances.

Although the UK has not yet fully adopted the metric system, we are slowly beginning to do so. And when you consider the ease with which grams convert to milligrams, centimeters to meters, and meters to kilometers, it is easy to see why most of the world uses the metric system as the standard measurement system!