The Metric System is an international system of measurement that was invented by two French scientists in 1795. It is also sometimes referred to as “SI” or “SI System”, which are abbreviations for the French translation, Système Internationale.

It has been officially adopted by most countries in the world because it is an easy-to-convert decimal system. The USA, however — along with Liberia and Myanmar — does not use the Metric System. It uses the Imperial System instead. But why is this? In this article, we’ll explain all.

In the USA, you will come across metric measurements like kilometers and grams, but Imperial is the preferred system of measurement that’s used in the country.

Some argue that this sets the USA apart from the rest of the world as it symbolizes the country’s status as a leader instead of a follower. However, the main reasons the USA hasn’t adopted the Metric System have to do with time and money.

Continue reading to find out more.

Why would it be expensive and time-consuming for the USA to use the Metric System?

The Imperial System has been used in the USA since the beginning of the Industrial Revolution. This means that all the machinery in manufacturing plants has been developed to measure in imperial units. To change all this machinery over to the Metric System would take a long time and cost a lot of money.

Additionally, while the Metric System is taught alongside the Imperial System in schools (you will see both centimeters and inches on classroom rulers), many American citizens would need to take time to familiarize themselves with the new measurements.

What units of measurement are used in the Metric System?

The Metric System is based on the meter for length and the kilogram for mass. Some of the other metric units of measurement include:


  • Kilometer
  • Centimeter
  • Millimeter


  • Gram
  • Milligram


  • Liter
  • Milliliter
  • Centiliter


  • Celsius

Some not-so-common metric measurement units are the ampere, which is used to measure electric current; the mole, which is used to measure the amount of a substance; and the candela, which is used to measure the visual intensity of light sources.

What units of measurement are used in the Imperial System?

Before we list some common imperial units of measurement, you might find it useful to know that there are two types of imperial measurement systems. As well as the United States Customary System, there’s the British Imperial System. 

From 1824 to 1965, this was the British Imperial System was the UK’s official measurement system. The reason it was developed was because units, such as pound and foot, meant something different depending on where you were in the country. A standardized way of measuring was needed to unite the country, so the British Imperial System was introduced.

The United States Customary System is based on the British Imperial System. However, there are some key differences between the units of measurement. For example, a British pint is equal to 20 fluid ounces, while a USA pint is equal to 16 fluid ounces, and the British stone isn’t used in the USA.

Some of the common imperial units of measurement include:


  • Inch
  • Foot
  • Yard
  • Mile


  • Ounce
  • Pound
  • Ton


  • Pint
  • Quart
  • Gallon


  • Fahrenheit

Which is better, the Metric System or the Imperial System?

Many people argue that the Metric System is better because it is more logical than the Imperial System. As mentioned earlier, the Metric System is based on decimals, which is why most of the world’s countries have adopted it.

A decimal system is easy to understand because when you move a number’s decimal point one place to the left or right, you simply divide that number by ten. Converting between metric units makes more sense than converting between imperial units, and the conversions are much easier to remember. For example, one kilometer equals one meter, and one meter equals 100 centimeters, whereas one yard equals three feet and one foot equals 12 inches.

Here are some other reasons why the Metric System is better than the Imperial System:

  • Metric calculations can be displayed in decimals on automatic calculators 
  • Fractions can be expressed in decimal form and vice-versa
  • There are only around 30 individual metric units — and most of these are only used in specialized fields
  • The Metric System isn’t based on the body parts of people from centuries ago like the Imperial System is
  • They may not strictly be imperial units of measurement, but cups and tablespoons aren’t as precise as grams because the tools used to measure can differ slightly, and the amount can vary depending on how tightly the substance is packed

How do you convert metric units to imperial units?

If you need to convert metric units to imperial units — and vice versa — the easiest way is to use an online calculator. Additionally, here is a table of some typical metric-to-imperial conversions:

Metric unitImperial unit
30.48 centimeters1 foot
1 centimeter0.39 inches
2.54 centimeters1 inch
1.609 kilometers1 mile
0.9144 meter1 yard
1 meter39.37 inches
0.093 square meter1 square foot
2.590 square kilometers1 square mile
0.405 hectare1 acre
0.454 kilogram1 pound
1 kilogram2.2 pounds
1 gram0.035 ounces
28.350 grams1 ounce
0.907 metric ton1 short ton
1 liter33.814 ounces
3.785 liters1 gallon
29.573 milliliters1 ounce
0.473 liters1 pint
0.946 liters1 quart
130 degrees Celsius250 degrees Fahrenheit 
150 degrees Celsius300 degrees Fahrenheit
190 degrees Celsius375 degrees Fahrenheit
200 degrees Celsius400 degrees Fahrenheit
230 degrees Celsius450 degrees Fahrenheit

It is not completely accurate to say that the USA doesn’t use the Metric System. While the Imperial System is the country’s official system of measurement, metric units are taught in schools, and you will see them in everyday situations, such as on food nutrition labels and in sporting events. The Metric System is also used extensively in fields like science so that theories, experiments, and ideas can be shared and understood quickly and easily with others around the world.