Correct Use
 When the United Kingdom was colonizing the globe during the 18th Century, they brought with them their English system, also known as the imperial system.
 One of their then main colonies, the United States, adapted this unified system of measurement and formalized it as the United States customary units, which are still in use today.
 During the 19th Century, continental Europe created the metric units that primarily rely on a decimal system (with the base number ten), known as the metric system.
 Almost every country uses the metric system, except for the United States and its former colonies, Liberia and Myanmar (also known as Burma) .
You might have realized that people from the US use different measuring units compared to almost anywhere else in the world. But why is that, and how can we cope with the differences these fundamental systems entail? Let’s have a look at the imperial system and the metric system in this article.
Why Are There Two Measurement Systems for Length, Volume, and Mass?
Back in the day, when the world wasn’t as interconnected as nowadays, every country—sometimes every region—had its own units of measurement. Obviously, this caused problems in trading. Imagine that a pound from your perspective was much more weight than it was for the other person.
When the United Kingdom was colonizing the globe during the 18th Century, they also brought their English system with them. That is the reason for still calling it the imperial system. The United States, one of Britain’s main colonies, directly adapted this unified system of measurement. In 1832, the US officially formalized the socalled United States customary units, which are still in use today.
During the 19th Century, continental Europe created the metric units that primarily rely on a decimal system (with the base number ten). Using meter as the basic unit for length, it was defined, for example, that the distance between the North Pole and the equator is exactly 10,000 kilometers running through Paris.
Almost every country has adapted this measurement system since then. Only the US as well as its former colonies Liberia and Myanmar (also known as Burma) still use the imperial system almost entirely. The UK (plus its overseas territories) and Canada use both systems in parallel.
What Is the Difference Between the Metric and the Imperial System?
The metric system and the imperial system use different units for length, area, volume, and mass. While the metric system is based on scaling with steps of 10, defining the measurement units in the imperial system is more complex.
Length in metric system  Length in imperial system 



These are the most common units in our daily life. The abbreviations in the metric system don’t use periods, while American units use periods in their abbreviated forms. All units are written in lowercase.
It is worth noting that there are more units, or modifications in use (like nanometer, decimeter, pica, point, miles per hour, kilometer per hour, etc.). Miles are also found in nautical distances, but a nautical mile is a little longer than a (land) mile (1.15 miles).
Area in metric system  Area in imperial system 



The units for area show the same steps as length units, as an area of 1 square meter consists of 1 m × 1 m, for instance. The imperial system shows more complexity, again.
Weight in metric system  Weight in imperial system 



The mass units show some logical scaling in the imperial system. The metric system relies on steps of 1,000 this time.
Remember that the unit ton exists in both systems: 1 ton in the US equals roughly 9 metric tons. Furthermore, the word pound appears unofficially in the metric system—weighing exactly 500 grams—as well as in many currencies (e.g., Pound Stirling).
Although not part of the United States customary units, the imperial unit of stone (no plural form) is used by the British when referring to body weight. One stone is exactly 14 lbs. (so roughly 6.4 kg).
Liquids in metric system  Liquids in imperial system 



There are many more units for liquids (e.g., barrel, teaspoon, tablespoon, cubic meter, cubic feet, minim, dram) in use. Pay attention with the unit pint, since there is also an American pint (which is less than the British equivalent).
Is It Possible to Change Between the Two Systems?
The real challenge is to convert data from one system to the other one. This process is highly complex, but we want to show you some rules of thumb. Coming from America to another part of the world (or vice versa) these mnemonic strategies might help you to adjust:
 Think of a ruler from school. The long ones usually indicate 30 centimeters, or roughly 1 foot. Almost the same number applies to the correspondence between inches and millimeters: 1 inch = 25 millimeters.
 1 mile is the same as 1.6 kilometers. You can remember this by considering the age of most Americans when they’re allowed to drive: 16 years.
 One soccer field is about 7,100 square meters. Switch the numbers around, and you’ll get the size in acres: 1.7.
 In America, you weigh (nearly) twice as much, since your scale is now in pounds, and not in kilograms anymore. The average American person weighs around 200 lbs., which is slightly more than 90 kg (or 14,23 stone in the UK).
 The average British person is 1.71 meters tall. In the imperial system, this would correspond to 5 ft. 7 in. (5' 7''). Just remember, there are 5 digits in this equation, two times the 1, and two times a 7.
 1 quart almost exactly matches 1 liter. That is why both is true: a quarter of 1 gallon is a quart, and a liter equals the same as well.
 When it comes to ounces, just remember the number 30. In terms of mass, 30 grams are 1 ounce. In terms of liquid, 30 milliliters are 1 (liquid) ounce.
For any other conversion, please refer to unit converters like:
The future will show if the UK establishes “their old” unit system again, or if they just leave both systems in use. LanguageTool promotes internationality. If you activate picky mode, it will suggest mentioning the metric equivalent every time you use an imperial unit, in case you are writing for an international audience. LanguageTool has users all over the place, and we are certain that our readers might come from different backgrounds as well. This article has proven that it is hard to switch back and forth between the two systems.