Over the decades, people have used a short version of words, as well as some specific symbols in order to represent words and terms.

It has become part of our regular speech and writing.

You will rarely see people write kilometers or centimeters instead of km and cm, just because it is much easier that way, and people across the world are capable of understanding it.

That said, if you work in a multinational company for instance, and you have to send some reports, it is always easier to use symbols, since no matter where people are from, they will be able to understand your message.

We are here today to teach you how metric prefixes work, when to use each of them, and what symbols you could use.


Metric prefixes are commonly used prefixes that go before the basic words used for measurement.

They are there to tell us the exact amount of measure, which could be multiple units or just one small part of the unit.

Today it is very common to use metric prefixes for almost everything you can imagine, but one thing worth to note is that in the past people used a different kind of prefixes, devised to work with the binary system.


People have been using different kinds of things to measure everything since the dawn of men, and throughout the history, that process has evolved and with it came the need to have a unit for measuring that people could use when trading or building things.

That leads to the foundations of a system that was standardized and specialized to be used for that purpose, while also being perfectly recognizable to the people across the entire world.

That system is called the International System of Units or in short the SI Units.

Here, we will present to you two types of this system, physical SI units and electronics SI units.

1. Physical SI Units

Physical SI Units are used to measure units like time, mass, length etc.

There are several variations of measurements, depending on the country in which they are used, but the following physical SI units are pretty much standardized and are recognizable in every corner of the world.

  • Second (s) – used to measure time;
  • Meter (m) – used to measure length. While there are other units for measuring length, such as centimeter, inch, foot, mile, the meter is pretty much the very basic one, used everywhere;
  • Gram (g) – which is used to measure mass. Nowadays kilogram is often more used, but a gram is still the most basic unit in this regard;
  • Kelvin (K) – Kelvin is used to measuring temperature levels;
  • Newton (N) – standardized measuring unit for force.
Used for SI Unit Symbol
Time Second s
Length Meter m
Mass Gram g
Temperature Kelvin K
Force Newton N

2. Electronics SI Units

There are some very important measuring units that originate from electronics, which are commonly used and it is always good to know what they represent and when they are used.

  1. Volt (V) – it is used to measure electrical potential difference, or in other words, voltage;
  2. Ampere (A) – it measures the electric current;
  3. Watt (W) – used to measure the power of an electric product, such as light bulb;
  4. Joule (J) – used for measuring energy levels;
  5. Coulomb (C) – unit for measuring the electric charge;
  6. Ohm (Ω) – it shows the amount of electrical resistance;
  7. Farad (F) – it is used for measuring electrical capacitance;
  8. Henry (H) – used for measuring inductance;
  9. Hertz (Hz) – unit for measuring the frequency.
Used for SI Unit Symbol
Electric Potential Difference Volt V
Electric Current Ampere A
Power Watt W
Energy Joule J
Electric Charge Coulomb C
Resistance Ohm
Capacitance Farad F
Inductance Henry H
Frequency Hertz Hz


There are two types of metric prefixes, the one used to represent some higher amount of units and the second one, which is used to show us just the fracture of a single unit.

Let us first examine the metric prefixes used to measure multiple units.

1. Deca

First metric prefix we are going to discuss is deca. It is used to show us that there are ten times of some unit. It was adopted in 1795, which is way before the SI system has been founded.

It is not fairly used in common language, but it is still useful to have it when there is a need to express the measurement of some unit by tens.

2. Hecto

Hecto is sometimes referred to as hecta and is very used in particular fields, where large amounts of units are required for production so it would ease the writing process.

It represents a hundred units and, the same as deca; it was adopted in 1795 as well. The most common example of its use might be hl or hectoliter, but apart from that, it is used with some others measuring units as well.

3. Kilo

Kilo represents one thousand units and is very commonly used in almost every field of study, business and common life.

It was adopted in 1795, as well as deca and hector prefixes. Some of the most common usages of this prefix are in measuring of mass (kilogram), the length (kilometer), when measuring the power of the electricity (kilowatts) and to represent the small-sized files in computer science (kilobytes).

4. Mega

Mega is used to telling us there are one million units of something. It was adopted much later than previous prefixes, more specifically, in 1873, which was the year when the CGS system was introduced as well.

It is very used in several fields, especially in computer science, where it is used as a common prefix for units that measure the size of files and folders. In the past, it was used for more, but since computer science has evolved greatly since then, it is now used mostly for this.

5. Giga

Giga prefix shows us that there are one billion units and it was adopted a bit later than previously mentioned prefixes, more precisely in 1960 because the need for such a big number arose in several rapidly growing industries.

Its most common use is in computer science, where it is used to represent sizes of bigger files and some hardware characteristics, such as RAM memory, hard disk storage and GPU memory amongst other things.

6. Tera

Introduced the same year as Giga, meaning 1960, because of the rising need for numbers that would represent very large quantities of certain units, tera is used to tell us that there are trillion units of something.

It is used very much in computer science, as both hardware and software are getting more and more advanced every couple of years, so some of the most advanced computers have a very high system and GPU memory, as well as much more need for bigger hard drives, due to a lot of data.

7. Peta

Ok, now we are getting to the very big boys here. Peta is used to telling us that there are quadrillion units of something. It was introduced 15 years later than Giga and tera, meaning in 1975.

As you have probably figured it out by now, it is fairly used in computer science where it represents the very large amounts of bytes (petabyte), which tells us a lot about digital information we need.

You can probably guess that some of the most advanced computers in the world have this amount of data and hardware needs, like for example NASA equipment.

8. Exa

Same as peta prefix, eta was also adopted in 1975 and it is used to tell us that there is one quintillion of something, which is a very, very large amount.

As with the previous big prefixes, its most common use is in the computer industry where it is used to represent the amount of data stored. Let us give you some examples of how truly big this number is.

One exabyte of data is equal to two million personal computers completely filled with digital data, while five exabytes is the number which can represent the total number of words that have ever spoken by humankind.

And lastly, 15 exabytes equals the total amount of data that Google has had ever since its foundation.

9. Zetta

As we are getting closer to the biggest boy on this list, our mind is basically boiling with the number of zeros these numbers have.

Zetta is used to tell us that there are sextillion units of something. The term was adopted in 1991 and is basically used by very large IT companies or government and non-government institutions, such as NASA or some other agency.

In order for us to give you the idea of how big the number this prefix represent, let’s give you one example. One zettabyte equals to the size of around 250 billion DVDs, which is a hell of a lot if you ask me.

10. Yotta

And now, we have finally gotten to the prefix which represents the biggest number on the SI system list, which is yotta.

Yotta represents one septillion of units. Same as Zetta, it was introduced in 1991 and it is most commonly used in computer science to count the enormous amount of digital data stored on the internet.

One yottabyte equals the total size of the entire World Wide Web and some say that if you wanted to download all that data, you would need to spend 11 trillion years to do it, even with the fastest possible internet.


We have introduced you to the biggest boys in the prefix world, so right now it is time to show you some prefixes that show very small fractions of a unit, so let us get into it.

1. Deci

The biggest boy amongst these prefixes is deci. It is used to represent one-tenth of a unit and it was adopted when the initial list was made in 1795.

It is used in a lot of fields, so much that we could say that it is probably one of the most used prefixes from this list.

Some of the most common usages are deciliter, decibel, and decimeter, so you can find it almost anywhere as you can see.

2. Centi

Same as with deci prefix, centi was adopted in 1795 and was amongst the first prefixes used at the time of its making.

It represents one-hundredth bit of a single unit and is also very used in a lot of every-day products and activities.

Some of the most common usages of this prefix are centimeter and centiliter, but there are other known usages as well.

3. Milli

The last of 1795 family prefixes is, of course, mili. It is used to tell us that something is one-thousandth size of a full unit and is also one of the most used prefixes from this list.

Mili is used in several fields, as well as in every-day speech to represent very small things that are somewhat hard to notice.

The most common measurements that use this prefix are millimeter to show us tiny size of something, whether it is just a length or a measurement used in army ballistics, then we have milliliter and finally millisecond to represent very small fraction of a time, which is often used in high-speed car races or formula 1 championship.

4. Micro

Micro is another very commonly used prefix, which represents one-millionth bit of a single unit. It was adopted in 1873 when it was probably used to measure very small organisms and other things examined by microscope for example.

Apart from that, in modern times, it is fairly used in microbiology, computer science, and microengineering, where it is used to create tiny chips which are then implemented in further tech.

5. Nano

Adopted in 1960, a bit later than a micro prefix, nano is there to tell us that something is one billionth bit of a full-size unit.

There is some application of this prefix in several fields, some of which are very technologically advanced, such as computer science, biology, microengineering or chemistry.

In computer science and microengineering, it is used to signify very tiny objects, like chips, which have the ability to contain a large amount of data, even though they seem very small.

6. Pico

Pico is prefix used with measurements that show one trillionth bit of a unit. It was adopted the same year as nano prefix, meaning 1960 and it is used in more technologically advanced fields.

Since it represents the size of very small objects or organisms, this prefix could be used in computer science, physics, as well as in biology and microengineering.

For example, it could be used to measure the size of atoms, with the average size ranging between 60 and 520 picometers.

7. Femto

Adopted in 1964, 4 years later than pico and nano prefixes, at the 11th Conference on Weights and Measures, femto prefix is used to represent a quadrillionth bit of a whole unit.

It is often used in some natural sciences, such as different branches of physics, like quantum or nuclear physics, where it can signify some very small bits of a single unit, such as atoms, which is very important for scientists in order for them to get precise and clean data.

8. Atto

Atto prefix is used to signify a quintillionth bit of a unit. It was officially adopted at the same conference as femto, in 1964, just 4 years later than pico and nano prefixes.

As well as couple previous prefixes, atto has also found its use in physics and microbiology, where it is important to be able to give the exact number of measurement to a very tiny point of interests, such as atom and atom parts.

9. Zepto

As we have to get closer to the smallest possible things, it is getting harder and harder to find some specific comparison, because there aren’t that many miniature parts or even organisms, to begin with.

Zepto prefix is used to represent one sextillionth part of the unit, which is very small, even by small standards. The prefix was adopted in 1991, a bit later than atto and femto prefixes.

Some examples of its use could be that the electric charge of one electron contains around 160 zeptocoulombs and that the molecule found in insulin has a mass of around 10 zeptograms.

10. Yocto

Now we have reached the smallest among the smallest. Yocto is a prefix that signifies one septillionth bit of a unit and it was adopted in 1991, the same as zepto prefix.

It represents such a small measurement that it is considered even smaller than the smallest visible distance between two locations there is, which the Planck length is.

If the distance is smaller than the Planck length, it is considered to be the same location.


Each of these prefixes we defined has its own symbol and meaning, so we will combine everything we have said so far and put it in a single table so you could see the most basic information about all of these prefixes.

Name/Symbol Base 1000 Base 10 Scale Adopted in
Yotta/Y 10008 1024 Septillion 1991
Zetta/Z 10007 1021 Sextillion 1991
Exa/E 10006 1018 Quintillion 1975
Peta/P 10005 1015 Quadrillion 1975
Tera/T 10004 1012 Trillion 1960
Giga/G 10003 109 Billion 1960
Mega/M 10002 106 Million 1873
Kilo/k 10001 103 Thousand 1795
Hecto/h 10002/3 102 Hundred 1795
Deca/da 10001/3 101 Ten 1795
/ 10000 100 One /
Deci/d 1000-1/3 10-1 Tenth 1795
Centi/c 1000-2/3 10-2 Hundredth 1795
Milli/m 1000-1 10-3 Thousandth 1795
Micro/µ 1000-2 10-6 Millionth 1873
Nano/n 1000-3 10-9 Billionth 1960
Pico/p 1000-4 10-12 Trillionth 1960
Femto/f 1000-5 10-15 Quadrillionth 1964
Atto/a 1000-6 10-18 Quintillionth 1964
Zepto/z 1000-7 10-21 Sextillionth 1991
Yocto/y 1000-8 10-24 Septillionth 1991


Now that we have defined and examined all the prefix symbols, let us dig more into their usage in different fields.

1. Mass

When measuring mass, the most common prefixes are a kilogram, gram, milligram, and microgram. Even the ones that go smaller and often used, but when it comes to the prefixes which count multiple units, there is limited use of them.

So, you will rarely see megagram or gigagram in practice.

2. Volume

The similar could be said for volume measurement. Prefixes that indicate smaller units are often used in all fields, so you will almost always see liters, milliliters and microlitres. Centilitre and decilitre are commonly used in Europe for some daily products.

On the other side, prefixes that signify multiple units are not that common, because they are transformed into other words. For example, 1 kilolitre equals 1 cubic meter.

3. Length

When it comes to length, a lot of prefixes are used. You will often see kilometer, meter, centimeter, millimeter, and even the smaller ones.

When it comes to the ones showing very large numbers, they are rarely used and are changed with some non-metric units, such as light years.

4. Time and Angles

The most common ones are second, millisecond and microsecond. They are generally used in a lot of fields, with smaller ones being used primarily in sports like races, where every bit of a second matter.

5. Temperature

As for the temperature, people usually use Celsius or Fahrenheit, but if they wish, it is possible to put a prefix before that part, so, for example, you could say 21 millidegrees Celsius. But it is rarely seen and even if it is needed, the use of Kelvin is much more appropriate.

6. Energy

When it comes to energy, the use of prefixes is fairly often, especially with electrical energy consumption and power, like kW (kilowatts).

Apart from that, it is also used to measure your body energy, aka calories, so you could say that some food consists of 2kcal, which would mean it has 2 thousand calories.


Apart from their usage in the metric system, metric prefixes are also used outside of that very system. The most usual examples are megabyte and decibel.

One funny thing is that metric prefixes are also used by with currencies (megadollar), which does sound awkward but it is mostly used by scientists.


That was everything you need to know about metric prefixes, how and when they originated, what do they represent and which symbols to use to write them.

Now, all that remains is that you put up them to good use and maybe start that business you’ve ever wanted and sold a lot of kilograms of products.

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