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Units of Measurement

Growing up in Spain meant that I learned to use the International System of Units. Derived from the metric system, that is the official system of weights and measures throughout the world, except in Liberia, Myanmar, and the United States.

The International System of Units (SI) has seven base units:

  • meter (m) for length,

  • second (s) for time,

  • mole (mol) for amount of substance,

  • ampere (A) for electric current,

  • kelvin (K) for temperature,

  • candela (cd) for luminous intensity, and

  • kilogram (kg) for mass.

There are the 22 derived units, which are formed by powers, products, or quotients of the base units. Examples include degree Celsius (°C), watt (W), hertz (Hz), lux (lx), sievert (Sv), etc.

MORE: SI Derived Units

Some units are not considered part of the SI Units, but their use is accepted, such as the:

  • minute (min), hour (h), and day (d) for time;

  • degree (°), minute (′), and second (′′) for plane and phase angles; and

  • liter (l or L) for volume.

CHECK: Non-SI Units Accepted for Use with the SI

Finally, prefixes are added to unit names to produce multiples and sub-multiples of the original unit. All metric prefixes indicate that the unit has either been multiplied or divided by a factor of ten.

Therefore, one can say that the International System of Units is logical and convenient as no conversion tool is needed. Converting units is made simple with the use of decimals.

VISIT: Decimal Multiples & Sub-multiples of SI Units

Relocating to the US saw me adopting the United States customary units. This system is often incorrectly referred to as Imperial System. Like the US customary units, the Imperial System was developed from the so-called English units. Albeit similar, the Imperial System is currently only used in the United Kingdom along with the metric system.

At first, I couldn't make sense of the US customary units due to my "metric mentality." I tried converting units from one system to the other. However, I quickly realized that it would be easier to learn to measure life differently and not try to make sense of it or find equivalents.

MORE: Introduction to US Customary Units

Although I probably won't get exact matches unless I use a calculator or a converter, I've managed to establish close connections between the two systems.

For instance, I was hiking last week when a good friend of mine from Barcelona called. She asked me how the weather was. I knew the temperature was around 60 °F. Had I told her that, she wouldn't have known the equivalent in Celsius unless she used a converter.

I could have taken the time to convert it but gave her instead what I believe was the approximate equivalent. Therefore, I said that the temperature was around 16 °C, which is close to the actual equivalent of 15.6 °C for 60 °F.

CHECK: Customary Unit Conversions

Guessing, however, is not always a good approach. Here in America, people use customary units in commercial activities and personal and social use.

In certain industries, such as science and medicine, metric units are used instead. In my profession, I have to choose between the two systems based on the recipient of my translation work:

  • If the translation is for the American public, I use US customary units. In some cases, I have to put the metric equivalent as well.

  • If not, I will only work with metric units as that's what most of the world use, as well as in my fields of specialization.

Unless I've been specifically asked to do it, I will not make unit conversions myself. As a translator, I only work with what my clients give me. If I need more data, I will ask my clients for it. Converting units without guidance may lead to inaccuracies, so that's why I prefer to avoid it.

If it's so widespread, why do we keep resisting the metric system in the US?

The truth is that the metric system is already used in the US. While customary units are still seen alongside metric units on product labels, it's common for the goods themselves to be made using metric-based manufacturing processes. That's especially true when the goods are manufactured outside of the US.

In the 19th century, the US Congress proposed that the country transition toward the metric system. However, American industrialists had already stocked their factories with equipment based on the US customary units. To avoid the cost of adapting and replacing their equipment, those industrialists began using their influence to stop Congress from adopting the metric system.

In 1975, The Metric Conversion Act was passed. It declared the metric system "the preferred system of weights and measures for US trade and commerce," but permitted the use of US customary units in all activities. Additionally, it stated that all conversion was to be "completely voluntary."

VISIT: Why isn't the US on the Metric System?

While most people in this country seem to prefer the US customary units, "metrication" already exists in some areas. One clear example is that the units that we use to measure time are purely metric.

Time will tell if the US will end up adopting the metric system entirely. What's known is that it could be a lengthy and costly process. I understand that the metric system may make more sense in science. Yet, there are also some advantages to the US customary units as these appear to be more human-scale and realistic.

I can personally see that advantage with temperature. I find that Fahrenheit degrees depict the actual temperature better without having to resort to decimals as much. For instance, the 30-40 °F range represents the transition between frozen to cold more accurately than that between -1.1 and 4.4 °C.

What do you think will happen? Will the US keep its own system? Or will we eventually let go and adopt SI units entirely?


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