What’s The Difference: Metric vs. Imperial

For anyone who’s tried to tighten a bolt on the fly, went to find a quart measuring cup only to realize you only have liters, or wanted to know a car’s horsepower measurement in mph rather than kph – you’ve probably realized that the two most common systems of measurement don’t exactly mesh well. In fact, if you’ve ever tried to convert the numbers, you’re probably aware, most frequently, that you end up with an odd fraction or extremely long series of numbers after the decimal point.

So, what’s the story with these clashing measurements and how did they come to be? Well, that is exactly what we have set out to answer in this guide. So, the next time you’re in the garage and you need swap out your standard wrench for one in millimeters or you’re traveling abroad and trying to accurately map out the distance from start to finish, you will both be able to complete your task accurately and understand a little bit of background as to why these systems exist, which is more appropriate for a given task, and more. The following is our explanation on the difference between the metric and imperial systems of measurement.

Metric is often touted as the better of the two systems of measurement. And while that is still up for debate, it should be noted that the Metric system is predated by the Winchester measure (the system that would become the Imperial system) by literally hundreds of years. In fact, the Metric system wasn’t standardized until 1799, when it was introduced by the French. It has since become, by far and large, the most commonly used system of measurement, having been made the official system in all but 3 countries – with a little bit of gray area in England (common folks still use Imperial measurements for some things).

The original goal of the Metric system was pretty basic and understandable: to get every region of the world on the same page in regards to distances, weights, and volumes. Not only would it help communication between regions, it would also standardize trading and commerce to a degree, as the weights and sizes of tradable goods would be the same across all regions. And it appears to have worked, considering that nearly all countries in the world have accepted it as their measurement system. In fact, a commonly accepted term that is often used in place of ‘Metric’ is ‘International System of Units.’

While all systems of measurement hinge on a core unit that is unavoidably arbitrary, the Metric system tries to simplify that in two ways: by operating on a base-10 (ten millimeters equals a centimeter, one hundred centimeters equals a meter, 1,000 meters equals a kilometer, etc.) and by having scaling units that are named after their core unit in accordance with what they are in relation to it.The system is one of the most user-friendly out there. For instance, the prefix ‘milli’ means ‘thousandth.’ So a millimeter is 1/1,000th of a meter. ‘Centi’ means ‘hundredth,’ therefore making a centimeter 1/100th. ‘Kilo’ means ‘thousand,’ so 1 kilometer is equal to 1,000 meters.

The scale works the same for the other measurements in this system. For instance, weight is measured in grams. Ten milligrams equals a centigram. Ten centigrams equals a gram. 1,000 grams equals a kilogram. You get the point. This also makes using Metric based tools a bit easier. For instance, the next size up from a 1mm wrench is a 2 mm, 2 mm goes up to 3 mmm, and so on ad infinitum. Whether you appreciate the Metric system or not, it’s undeniable that the system is one of the most user-friendly out there in regards to understandability.

You might be surprised to discover two things about the Imperial system of measurement. First: it was actually based on a system developed by the British in the late 15th century. And second: there are only three countries that still officially use the Imperial system of measurement – they are the United States, Liberia, and Myanmar (Burma). Surely, there are arguments both for and against following suit with the rest of the world, but the fact of the matter is this: whether you like it or not, the U.S. continues to use the Imperial system.

In order to understand the Imperial system, it’s important to have a grasp of that which came before it. You see, in 1495, something called the Winchester measure was put into place in England by King Henry VII – which, thusly, spread to the English colonies. Unfortunately, this system was based on seemingly arbitrary measurements that were convenient to people at the time. For instance, one of the units of measurement in this particular system was a bushel. A bushel is defined as two kennings. A kenning was comprised of two pecks. And a peck, finally, is equivalent to what we know of now as 2 gallons. A gallon, however, is defined as 231 cubic inches or, we kid you not, 1/8 bushels when dry. As you can see, the system is a bit circular and rather complicated, which is what they were trying to fix when instituting and standardizing the British Imperial system in 1824.

This system, however, was also based on measurements that were convenient at the time of its creation and, as such, can be a bit confusing in itself. The core unit of this system is the foot.A foot was originally measured – quite literally – by the length of a person’s foot. As you might imagine, a foot was originally measured – quite literally – by the length of a person’s foot (this was common as far back as the time of the Romans and, before them, the Greeks). Seeing as how that leaves a bit of wiggle room from person to person, the Imperial system standardized it as 12 inches (an inch being an arbitrary measurement in itself). The rest of the measurements were created accordingly. The same went for volume calculations, with the core unit being the fluid ounce, and weight having been based on a pound.

An easy way to differentiate the measurements of the Imperial system from those of the Metric is by paying attention to how those measurements appear in sizes smaller than an inch. You see, whereas the Metric system uses whole numbers with a letter denotation, the Imperial system uses fractions and, sometimes, symbols – a single set of quotes for inches and a single apostrophe for feet. For example, a quarter-inch wrench will appear as 1/4″. This denotation will help you more easily identify whether a tool is built in Metric or Imperial.

Generally speaking, it’s a safe bet to base all of your tools and measuring cups on the commonly accepted units of measurement in your particular place of residence. That does, however, come with exceptions. For instance, if you own a motorcycle that was built in Japan and you want to work on it, there’s a pretty good chance you’ll need metric wrenches. This is not, however, a given. Unfortunately, unless you are choosing the parts yourself, it’s going to be kind of a guess and check situation.It’s going to be kind of a guess and check situation. It can also be said that there’s a little bit of give between tools. For instance, a 3 millimeter wrench is only slightly smaller than a 1/8 inch. So, if you have a bolt that measures at 3 millimeters, you can actually get away with using a 1/8-inch wrench to tighten or loosen it. It’s not perfect and you could end up stripping the bolt with repetition, but it will generally work in a pinch.

The bigger point is this: there’s no good way to know in which system you can comfortably invest yourself. At least, not so long as there’s a global economy and not everyone is on the same page. You can generally assume that things made in metric-based countries will come in metric sized and that the same goes for stuff made in America being Imperial. But, it’s not something anyone can say with 100% certainty. The truth is, you’ll probably be the best off if you get yourself an array of tools that come in both formats. That way, rather than trying to fiddle one onto the other, you can just swap out for the appropriate size. In any case, you’ll want to do what’s best for you and your wallet. If you need to pull a MacGyver here and there, so be it. It’s not the end of the world. The same can be said for converting units. In fact, there’s a litany of apps and websites for it, if you don’t want to do it yourself. It’s not necessarily the most convenient, but it isn’t terribly difficult. Until everyone follows the same system of measurement, however, that’s just how things are going to be.

Horsepower vs. Torque

Now that you understand how measurements of distance relate to one another, find out how you’re traversing those distances in your car by learning the difference between torque and horsepower.