The Scale of Things - Nanometers and More. (Source: Office of Science, U.S. Department of Energy) (click on image to enlarge)
Metric Prefixes
Your guide to metric prefixes and conversion from yocto to yotta
Table of Contents
- 1. What are Metric Prefixes?
- 2. Capitalization of SI Prefixes
- 3. Conversions Between Metric System Units
- 4. Metric Prefix Table
- 5. Examples and Common Uses for Metric Prefixes
- 6. The Scale of Things – Nanometers and More
- 7. Secret Worlds: The Universe Within
- 8. Frequently Asked Questions about Metric Prefixes
Key Takeaways About Metric Prefixes
- Definition: Metric prefixes are standardized numerical multipliers placed before units of measurement
- Range: From yocto (10-24) to yotta (1024), covering 48 orders of magnitude
- Purpose: Make describing quantities more concise and provide a standardized way to express measurements
- Capitalization: Prefixes for multiples generally use uppercase symbols (except k, h, da); submultiples use lowercase
- Usage: Applied to all SI units (meters, grams, seconds, etc.) and commonly used in computing, physics, and other fields
- Conversion: Based on powers of ten, making conversions between metric system units straightforward
- Origins: Prefixes derive from either Latin or Greek terms and are specified by the International Bureau of Weights and Measures
What are Metric Prefixes?
A metric prefix is a numerical multiplier that is placed before a basic unit of measure to indicate a specified multiple or fraction of that unit. The 20 recognized metric prefixes have been specified by the International Bureau of Weights and Measures (BIPM) for the International System of Units (SI), and are used to make describing quantities more concise.
These prefixes range from the smallest, "yocto" (1 quadrillionth), to the largest, "yotta" (1 quadrillion), and provide a standardized way to express quantities in a way that is easily understood and comparable.
These prefixes are utilized with various metric units of measurement, including but not limited to mass, volume, weight, length, time, temperature, angle, and energy. They provide a convenient way to express quantities in a standardized manner, allowing for easier comparison and communication between individuals.
In addition to their use within the metric SI system, metric prefixes are also commonly used outside of it in many different fields. For example, the prefix "giga" is used in the term "gigabyte" in computing, "mega" in "megaparsec" in astrophysics, and "mega" in "megaelectronvolt" in particle physics.
Capitalization of SI Prefixes
SI prefixes for submultiples (smaller quantities or sub units) are formatted with all lowercase symbols while prefixes for multiples (larger quantities or whole units) use uppercase symbols with the exception of three: kilo (k), hecto (h) and deka (da). So a gigahertz is GHz and a femtosecond is fs.
Conversions Between Metric System Units
Conversions between metric system units are easy because the system is based on powers of ten. For example, there are 100 centimeters in 1 meter, 1000 meters in 1 kilometer. Conversely, there are 1 billion nanometers in 1 meter. Metric prefixes are used to distinguish between units of different size. These prefixes all derive from either Latin or Greek terms.
The table below lists the most common metric prefixes and their relationship to the central unit that has no prefix. Length is used as an example to demonstrate the relative size of each prefixed unit.
Metric Prefix Table
Prefix
Symbol
Multiplier
Exponential
yotta
Y
1,000 000 000 000 000 000 000 000
1024
zetta
Z
1,000 000 000 000 000 000 000
1021
exa
E
1,000 000 000 000 000 000
1018
peta
P
1,000 000 000 000 000
1015
tera
T
1,000 000 000 000
1012
giga
G
1,000 000 000
109
mega
M
1,000 000
106
kilo
K
1,000
103
hecto
h
100
102
deca
da
10
101
1
100
deci
d
0.1
10-1
centi
c
0.01
10-2
milli
m
0.001
10-3
micro
µ
0.000 001
10-6
nano
n
0.000 000 001
10-9
pico
p
0.000 000 000 001
10-12
femto
f
0.000 000 000 000 001
10-15
atto
a
0.000 000 000 000 000 001
10-18
zepto
z
0.000 000 000 000 000 000 001
10-21
yocto
y
0.000 000 000 000 000 000 000 001
10-24
Examples And Common Uses for Metric Prefixes
Zetta Prefix
The estimated total annual amount of digital data created, consumed, and stored globally is about 64 zettabytes in 2020, expected to rise to 180 zettabytes by 2025.
Tera Prefix
A distance of one terameter is roughly one light hour. The diamter of Earth's orbit around the Sun is about 0.3 terameters
Terahertz radiation consists of electromagnetic waves within the ITU-designated band of frequencies from 0.3 to 3 terahertz (THz).
The hard disk capacity of modern computers has reached the terabyte range.
Giga Prefix
The clock speeds of CPUs in modern computers has reach the gigahertz (GHz) range.
Mega Prefix
Megapixels are commonly used to express the number of image sensor elements of digital cameras or the number of display elements of digital displays.
Kilo Prefix
Widely used for distance (kilometer) or weight (kilogram).
Milli Prefix
The head of a pin is about 2 millimeters in diameter. The smallest distances the human eye can resolve is around 0.02 to 0.04 mm. Red ants are about 5 mm long.
Micro Prefix
Also expressed by the Greek letter µ. Biology often deals with objects in the micrometer range such as bacteria (1-10 µm), red blood cells (7-8 µm), pollen (&sim 100 µm) or mites (&sim 500 µm).
Nano Prefix
A strand of human DNA is 2.5 nanometers in diameter. A single gold atom is about a third of a nanometer in diameter
Pico Prefix
The Bohr diameter of hydrogen atom in ground state is 106 picometers
Femto Prefix
The diameter of a proton is 1.6 femtometers. Molecules react within femtoseconds. The light pulses produced with the most modern lasers last just a few femtoseconds to attoseconds
Atto Prefix
Attosecond physics deals with ultrafast processes in nature. For instance, the motion of electrons in atoms lasts just a few attoseconds.
The Scale of Things – Nanometers and More
Take a look of examples across a range from centimeter to nanometer:
Secret Worlds: The Universe Within
View the Milky Way at 10 million light years from the Earth. Then move through space towards the Earth in successive orders of magnitude until you reach a tall oak tree. After that, begin to move from the actual size of a leaf into a microscopic world that reveals leaf cell walls, the cell nucleus, chromatin, DNA and finally, into the subatomic universe of electrons and protons.
(Secret Worlds: The Universe Within. © Michael W. Davidson and The Florida State University)
Once the tutorial has completely downloaded, a set of the arrows will appear that allow the user to increase or decrease the view magnitude in Manual mode. Click on the Auto button to return to the Automatic mode.
Notice how each picture is actually an image of something that is 10 times bigger or smaller than the one preceding or following it. The number that appears on the lower right just below each image is the size of the object in the picture. On the lower left is the same number written in powers of ten, or exponential notation. Exponential notation is a convenient way for scientists to write very large or very small numbers.
Frequently Asked Questions about Metric Prefixes
What are the 20 metric prefixes?
The 20 recognized metric prefixes in the International System of Units (SI) are, from largest to smallest: yotta (Y), zetta (Z), exa (E), peta (P), tera (T), giga (G), mega (M), kilo (k), hecto (h), deca (da), deci (d), centi (c), milli (m), micro (μ), nano (n), pico (p), femto (f), atto (a), zepto (z), and yocto (y).
Who decides on metric prefixes?
Metric prefixes are specified by the International Bureau of Weights and Measures (BIPM) for the International System of Units (SI). This international standards organization ensures consistency in measurement across the globe.
Why are metric prefixes important?
Metric prefixes allow us to express very large or very small quantities in a concise and standardized way, making scientific communication clearer and more efficient. They eliminate the need to write out long strings of zeros and provide a universal language for measurement across different fields and countries.
How do you convert between metric prefixes?
To convert between metric prefixes, multiply or divide by powers of 10. For example, to convert from kilometers to meters, multiply by 1,000 (103); to convert from nanometers to meters, divide by 1,000,000,000 (10-9). This power-of-ten relationship makes conversions straightforward.
Are there any new metric prefixes being considered?
As of 2022, the International Bureau of Weights and Measures (BIPM) approved four new prefixes: ronna (R) for 1027, quetta (Q) for 1030, ronto (r) for 10-27, and quecto (q) for 10-30. These additions extend the range to accommodate increasingly large (data science) and small (quantum physics) measurements.
What's the difference between SI prefixes and binary prefixes?
SI prefixes (kilo, mega, giga, etc.) are based on powers of 10, while binary prefixes (kibi, mebi, gibi, etc.) are based on powers of 2. Binary prefixes were introduced to resolve ambiguity in computing where kilo traditionally meant 1,024 (210) rather than 1,000 (103). For example, 1 kibibyte (KiB) = 1,024 bytes, whereas 1 kilobyte (KB) = 1,000 bytes.
Why do some prefixes use uppercase symbols and others lowercase?
Prefixes for multiples (larger quantities) generally use uppercase symbols, while prefixes for submultiples (smaller quantities) use lowercase symbols. There are three exceptions to this rule: kilo (k), hecto (h), and deka (da), which use lowercase despite being multiples. This convention helps distinguish between similar-looking symbols, such as mega (M) and milli (m).
What does the micro symbol (μ) look like?
The micro symbol (μ) is the Greek letter mu in lowercase. It looks similar to a lowercase 'u' with a small tail on the left side. In computing contexts where Greek letters may not be available, it's sometimes substituted with 'u' or 'mc', though this is not officially recognized.
