What are Prefixes in Physics? 

A prefix in physics simply refers to the addition of a letter or symbol to an s.i unit or physical quantity in order to shorten its figures for better understanding. They are group of letters or symbols that are added to the beginning of a unit of measurement to represent a multiple or fraction of the standard unit. For example, kilo- means 1000, and milli- means 1/1000. Prefixes are based on powers of 10, making it easier to work with very large or small numbers. To simplify the definition, we can say that a prefix is always added before the unit and after the figures. 

prefixes in physics
prefixes in physics

In physics, we use prefixes to represent very large or small values of physical quantities. They make it easier to work with values that are either too large or too small to be expressed in the standard unit of measurement. We commonly use prefixes in scientific notation and they are very important in physics.

For an answer to be considered a prefix, it must contain a large figure that might look inappropriate to fit in as the final answer or into your calculation (because it will look cumbersome).

For Example, 0.00000789 may look inappropriate in a calculation. 

Instead, it’s converted into a standard form or to the power of 10. For example, 7.89 x 10-6. It is important to know that the power of 10 may turn out to be negative or positive depending on what you are dealing with. Therefore, after writing 7.89 x 10-6 we will need to still shorten the figures by adding a prefix. Assuming it’s in Faraday, we can then write it as 7.89 x 10-6 F. Hence, to add a prefix, we now say that 10-6 = micro = μ 

Thus, we can now replace 10-6 as micro = μ, by adding our prefix before our unit which implies, 7.89 μF = 7.89 micro faraday

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Physics Practical

Table of Prefixes: What are Prefixes in Physics

Below is table of prefixes in physics

PrefixStandard formCurrent symbol
A table of prefixes in physics

List of common prefixes

The most commonly used prefixes in physics are:

  • Kilo- (k): 1000
  • Mega- (M): 1,000,000
  • Giga- (G): 1,000,000,000
  • Milli- (m): 1/1000
  • Micro- (μ): 1/1,000,000
  • Nano- (n): 1/1,000,000,000

History of Prefixes

We have 20 sets of prefixes that are accepted and being used for measurement globally. We started applying this form of the metric system after an agreement was reached in 1960. In 2022, a British meteorologist (Richard J. C. Brown) came up with the idea of four more additional prefixes, and they are quetta, ronna, ronto, and quecto. These prefixes were added to the list of the existing prefixes we already have. 

Also, ronna and quetta are mostly used in data science. Additional prefixes are ronto (10-27) and quecto (10-30). You also need to understand that joining two prefixes at the same time is not approved in Physics. For example, writing HECTOMEGAGRAM does not make sense and should be avoided. In 1975, France was measuring units by applying Greek terms like myriad (10,000), double (2), and demi (½)

How to Write Prefixes in Physics 

Here is how to write prefixes in physics:

  • Write the figures you have obtained or given. For example, 20,000
  • Find the symbol of the prefix. For example, c is for centi. Centi represents ten to the power of minus two (2).
  • The symbol of the unit you are calculating. For example, a meter is a unit of length
  • Add the three together. The figure comes first, followed by the prefix, and then the unit. For example, 200cm is the same as 20,000(1/100)m.

Conversion Between Units

Prefixes are used to convert between different units of measurement. For example, one kilometer (km) is equal to 1000 meters (m), and one millimeter (mm) is equal to 1/1000 of a meter (m). To convert between units, simply multiply or divide the value by the appropriate prefix. It is important to use the correct prefix when making conversions to ensure that the value is expressed in the correct unit.

What is the Unit of Length For Angstrom, Light Year, and Micron

Here are some units of length with prefixes


This is one of the units of measurement for the length. The symbol of angstrom is Å, the capital letter A with a sign of degree on top of the letter. One angstrom (1Å) is equal to 0.0000000001 or 10-10m (which is in standard form). We can equally say that 1Å is equal to 0.1 nanometers (nm).

We use angstrom to measure variables like sizes of molecules, atoms, wavelengths of X-rays, wavelengths of gamma rays, or wavelengths of ultraviolet rays (UV – rays). Additionally, the size of the helium atom is about 1Å (10-10m). The diameter of the nucleus of a helium atom is about 1 ferrometer (10-15m). Angstrom is no longer in use as before. The symbol Å came from Swedish letters. Angstrom was adopted in 1907 and is not an S.I. unit of measurement. Nanometer and picometer are constantly used instead of angstrom.


The speed of light is beyond our imagination, this is because light covers 11 million miles in just a minute. It takes 365 days to make cover a distance of one light-year. We can now define a light year as the distance covered by a beam of light in 365.3 days. The distance covered by the beam of light in 365.3 days is about 9.5 trillion kilometers or 5.9 trillion miles. Light can travel as per as 11 million miles per minute, and the distance from the earth to the sun is close to eight light minutes.

It is obvious that we need to apply the knowledge of prefixes to be able to obtain an accurate distance covered by the beam of light. A light year is not an S.I. unit of measurement. Research has shown that light travels 670,616,629 miles per hour or 1,079,252,849 kilometers per hour.

How to Find a Light Year

The number of hours in a year = 8,766 hrs

Distance traveled by a beam of light per hour = 670,616,629 miles or 1,079,252,849 kilometers

The distance traveled by one light year = The number of hours in a year x Distance traveled by a beam of light per hour

This is now equivalent to Calculating light year In Miles

The distance traveled by one light year in miles = 670,616,629 miles/hr x 8,766 hrs = 5,878,625,369,814 miles

Therefore, One light-year = 5,878,625,369,814 miles which are approximately 5.9 trillion miles

It is obvious that we need the knowledge of a prefix to conveniently work with the above figures.

Calculating light year In Kilometers

The distance traveled by one light year in kilometers = 1,079,252,849 km/h x 8,766 hrs = 9,460,730,474,334 km

This shows that one lightyear in kilometers = 9,460,730,474,334 kilometers and can be approximated as 9.5 trillion kilometers

We can also see that it is easy to employ the knowledge of prefixes in physics in the above context to make our work easier

For example, the diameter of the milky way galaxy is about 2 x 105 light-years. Additionally, the distance between the nearest galaxy (Andromeda) to the earth is about 2.5 million light-years

Application of Micron in Prefixes

Micron is also known as 1 x 10–6. You can see that a micron has the same value as a micrometer. Scientists are currently using micrometers instead of microns in their work. The symbol for the micron is the same as the symbol for the micrometer which is μ (Miu). The diameter of red blood cells is about 10 microns. Additionally, the diameter of human hair is about 10 to 102 microns

Standard Form of Prefixes in Physics

Here is more clarification about the standard form of prefixes:

Yotta = Y = 1024 = 1,000,000,000,000,000,000,000,000

Zetta = Z = 1021 = 1,000,000,000,000,000,000,000

Exa = Z = 1018 = 1,000,000,000,000,000,000

Peta = P = 1015 = 1,000,000,000,000,000

Tera = T = 1012 = 1,000,000,000,000

Giga = G = 109 = 1,000,000,000

Mega = M = 106 = 1,000,000

Kilo = K = 103 = 1,000

Hecto = h = 102 = 100

Deca = da = 101 = 10

Deci = d = 10-1 = 0.1

centi = c = 10-2 = 0.01

milli = m = 10-3 = 0.001

micro = μ = 10-6 = 0.000001

nano = n = 10-9 = 0.000000001

pico = p = 10-12 = 0.000000000001

Femto = f = 10-15 = 0.000000000000001

Atto = a = 10-18 = 0.000000000000000001

Zepto = z = 10-21 = 0.000000000000000000001

Yocto = y = 10-24 = 0.000000000000000000000001

These are the names of prefixes, their symbols, standard form, and in decimal places.

Note: Ten to the power of zero (100) is one according to the law of indices. Therefore, 100 = 1.

How to Write Prefixes in Physics

Here is how to apply prefixes in physics:

Yotta: we can write yotta as 0.8 YW = 0.8 Yottawatts

Zetta: we can write zetta as 4.2 Zs = 4.2 Zettaseconds

Exa: we can write Exa as 1.5Ekg = 1.5 Exakilogram

Peta: we can write Peta as 6.7Ps = 6.7 Petaseconds

Tera: we can write Tera as 0.3Tm = 0.3 Teramiles

Giga: we can write Giga as 10 Gb = 10 Gigabytes

Mega: we can write Mega as 30 MW = 30 Megawatts

Kilo: we can write Kilo as 20kg = 20 kilogram

Hecto: we can write Hecto as 55 hm = 55 hectometers (No longer in use by SI)

Deca: we can write Deca as 100 daL = 100 decaliters (No longer in use by SI)

Deci: we can write Deci as 90 dm = 90 decimeters (No longer in use by SI)

Centi: we can write Centi as 70 cm = 70 centimeters (No longer in use by SI)

Milli: we can write Milli as 25 mm = 25 millimeters

Micro: we can write Micro as 35 μF = 35 micro-faraday

Nano: we can write Nano as 28 nm = 28 nanometer

Pico: we can write Pico as 1.2 pA = 1.2 picoamperes

Femto: we can write Femo as 5.3 fs = 5.3 femtoseconds

Atto: we can write atto as 2.5 ag = 2.5 attogram

Zepto: we can write Zepto as 0.8 zm = 0.8 zeptometer

Yecto: we can write Yecto as 3 ys = 3 yoctoseconds

Applications in Physics

Prefixes are used in various areas of physics, such as astronomy, nuclear physics, and particle physics. For example, the distance between stars is measured in light-years, which is a unit of distance equal to the distance that light travels in one year. One light-year is approximately equal to 9.46 x 1012 kilometers (km). Prefixes are also used to express the mass of subatomic particles, such as protons and electrons, which are measured in units of kilograms (kg) or electron volts (eV).

Examples of the Application of Prefixes in Physics

In addition to what I explained, here are some examples in a table to help you understand the applications of prefixes in physics:

PrefixSymbolStandard formUnitAbbreviationStandard form + UnitApplication
exaE1018exameterEm1018 mdistance light travels in a century
petaP1015petasecondPs1015 s30 million years
teraT1012terawattTW1012 Wpowerful laser output
gigaG109gigahertzGHz109 Hza microwave frequency
megaM106megacurieMCi106 Cihigh radioactivity
kilok103kilometerkm103 mabout 6/10 mile
hectorh102hectoliterhL102 L26 gallons
dekada101dekagramdag101 gteaspoon of butter
100 = 1deciliter
decid10−1centimeterdL10−1 Lless than half a soda
centic10−2centimetercm10−2 mfingertip thickness
millim10−3millimetermm10−3 mflea at its shoulders
microµ10−6micrometerµm10−6 mdetail in microscope
nanon10−9nanogramng10−9 gsmall speck of dust
picop10−12picofaradpF10−12 Fsmall capacitor in radio
femtof10−15femtometerfm10−15 msize of a proton
attoa10−18attosecondas10−18 stime light crosses an atom


Also, here are some important points you may need to know

Distance to boundary of observable Universe is 1 x 1026 m

The distance to Andromeda galaxy (a) is 2.1 x 1022 m

We also have diameter of our Galaxy as 7.6 x 1020 m

Distance to nearest star (Proxima Centauri) is 4 x 1016 m

Earth–Sun distance is 1.5 x 1011 m

Radius of Earth is 6.4 x 1016 m

Wavelength of radio wave (AM band) is 3 x 102 m

Length of ship Queen Elizabeth is 3.1 x 102 m

Height of average human male is 1.8 m

Diameter of red blood cell (human) is 7.5 x 10-6 m

Wavelength of visible light is approximately 5.7 x 10-7 m

Diameter of smallest virus is 2 x 10-8 m

The diameter of atom is 1.0 x 10-10 m

Diameter of atomic nucleus (iron) is 8.0 x 10-15 m

We also have the diameter of proton as 2 x 1015 m

Multiples and Submultiples of the Foot

Mile = One (1) mile is equal to 5280 feet which is equivalent to 1609.38 meters

Yard (yd) = One (1) yard is the same thing as 3 feet which is equal to 0.9144 meters

Foot (ft) = One (1) feet is equal to 0.3048 meters

Inch (in.) = One (1) inch is equivalent to (1/12) feet which is also equal to 2.540 centimeters

mil = 1 mil = 0.001 inch

10 Examples of Prefixes in Physics

Here are 10 examples of prefixes commonly used in physics:

  1. Kilo-: A prefix denoting a factor of a thousand, often used with units like kilograms (kg) or kilometers (km).
  2. Mega-: Signifying a factor of a million, it’s found in units like megawatts (MW) or megahertz (MHz).
  3. Giga-: Represents a billion-fold increase, used in contexts like gigabytes (GB) or gigajoules (GJ).
  4. Tera-: Denotes a trillion-fold increase, seen in terabytes (TB) or terawatts (TW).
  5. Micro-: Indicates one millionth of a unit, as in micrometers (μm) or microseconds (μs).
  6. Nano-: Refers to one billionth of a unit, used in nanometers (nm) or nanoseconds (ns).
  7. Pico-: Represents one trillionth of a unit, seen in picometers (pm) or picoseconds (ps).
  8. Femto-: Denotes one quadrillionth of a unit, often used in femtometers (fm) or femtoseconds (fs).
  9. Centi-: Signifies one hundredth of a unit, found in centimeters (cm) or centiseconds (cs).
  10. Milli-: Indicates one thousandth of a unit, as in millimeters (mm) or milliseconds (ms).

Why do We use Prefixes in Physics?

Prefixes are used in physics to deal with large or small quantities more manageable and understandable. They help us to express measurements in a concise and clear manner, especially when dealing with large values. Imagine you have to describe the distance from one end of a city to another. Using just meters might result in a very large number, like millions of meters, which can be hard to say it with your mouth. By adding a prefix like “kilo-” (for kilometer), you can easily say the same distance as a more relatable number in kilometers.

Similarly, when we are dealing with tiny particles or extremely fast processes, using regular units like seconds or meters might lead to impractical numbers. Prefixes like “nano-” (for nanoseconds) or “micro-” (for micrometers) would help us to express these measurements in a way that is easier to work with. Therefore, prefixes simplify the representation of quantities which spans different orders of magnitude. They help us communicate effectively and make sense of the range of measurements encountered in physics.

Importance of Prefixes in Physics

Prefixes play a very important role in physics for several reasons. They help us in expressing measurements across a wide range of scales, from the smaller to the larger, in a more concise and understandable manner.

  1. Clarity and Comprehension: Prefixes help avoid writing out long strings of zeros when dealing with large or small numbers. This makes measurements and calculations easier to read and understand.
  2. Efficiency: Using prefixes reduces the need for excessive conversions between units. They streamline calculations and minimize errors.
  3. Precision: They enable us to represent quantities with appropriate levels of precision. For instance, using “millimeters” instead of “meters” for small lengths ensures accuracy.
  4. Communication: Prefixes facilitate effective communication among scientists globally, regardless of their native measurement systems, by providing a standardized way to express values.
  5. Versatility: Prefixes can be attached to various units, making them adaptable to different physical quantities. They can be attached to time (seconds), distance (meters), or energy (joules).
  6. Scientific Notation: Prefixes are an integral part of scientific notation. They are a concise way to represent very large or small numbers. They aid in theoretical calculations and data analysis.
  7. Research: In research, where measurements often span large scales, prefixes help scientists to work with numbers that would otherwise be difficult to quantify and understand.

How to Remember Prefixes in Physics

Remembering prefixes in physics can be made easier by applying these simple methods:

  1. Mnemonic Devices: Create mnemonic phrases or sentences using the first letters of prefixes in order. For instance, “King Henry Doesn’t Usually Drink Chocolate Milk” represents kilo, hecto, deka, unit, deci, centi, milli.
  2. Visual Associations: Visualize everyday objects or scenarios that match each prefix. For example, associate “kilo-” with a kilogram of sugar or “milli-” with a millipede.
  3. Flashcards: Create flashcards with the prefix on one side and its meaning on the other. Regular review will reinforce your memory.
  4. Grouping: Group prefixes by their powers of ten. Kilo, mega, and giga increase by powers of a thousand, while milli, micro, and nano decrease.
  5. Practice Problems: Solve physics problems involving different units and prefixes. Practice reinforces your memory and helps you apply prefixes in context.
  6. Online Resources: Utilize online quizzes, games, and interactive tools designed to help remember prefixes in an engaging way.
  7. Teaching Others: Teach prefixes to someone else. Explaining concepts to others enhances your understanding and memory.
  8. Repetition and Exposure: Regularly encounter and use prefixes in your physics studies. The more you encounter them, the more familiar they become.
  9. Storytelling: Create amusing or memorable stories that incorporate prefixes and their meanings.
  10. Analogies: Compare prefixes to familiar concepts. For example, liken “giga-” to “gigantic” or “micro-” to “microscopic” to remember their relative sizes.


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