The Metric System, it’s prefixes and how to convert between them.
A measurement made in the metric system, also known as SI (International System of Units) requires three parts.
- Numeric Value
- Prefix
- Unit of Measure
Numeric Value
The count of how many units are being referenced. This number will be a function of the prefix.
Prefix
Because using all the zeros in very large or very small numbers can be very cumbersome, the metric system utilizes the prefix to apply a numeric multiplier to a measurement so that you can more easily work with any number of any scale, large or small. Rather than trying to remember a specific multiplier by the number of zeros in it, that multiplier can be referenced by the prefix assigned to it.
Refer to the following chart to find value of a prefix.
Prefix | Symbol | Base 10 | Decimal |
---|---|---|---|
quetta | Q | 1030 | 1,000,000,000,000,000,000,000,000,000,000 |
ronna | R | 1027 | 1,000,000,000,000,000,000,000,000,000 |
yotta | Y | 1024 | 1,000,000,000,000,000,000,000,000 |
zetta | Z | 1021 | 1,000,000,000,000,000,000,000 |
exa | E | 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 |
100 | 1 | ||
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 |
ronto | r | 10−27 | 0.000000000000000000000000001 |
Notice how in the Base10 column we have 10 to a specific power. That is the number of positions the decimal has to move from Base 100. Also note, it does jump and not all positions have names. For example; micro to nano, even though the one proceeds the other, there is a gap of 3 decimal places.
“µ” , What is it and why?
The Metric System uses capital letters for prefixes that represent multipliers larger than 1,000,000 and lower case for those smaller. It also uses one letter prefixes which means that mega and milli had already taken the “M’s” It was decided that the Greek letter mu (µ) would be used to represent micro.
Most keyboards do not have a “µ” key. This means that using it can be difficult and why you will see it represented as regular “u” sometimes.
how to enter µ on your keyboard
For all keyboard layouts
-
On Microsoft Windows systems,
- arbitrary Unicode codepoints can be entered in hexadecimal as: Alt+0181; note that a leading “0” is required, or
-
On Linux systems,
- arbitrary Unicode codepoints can be entered in hexadecimal as: Ctrl+⇧ Shift+u b5space, or
For QWERTY keyboard layouts
- On Linux systems,
- code-point U+00b5 can be entered as right-alt+m (provided the right alt key is configured to act as
AltGr
).
- code-point U+00b5 can be entered as right-alt+m (provided the right alt key is configured to act as
- On MacOS systems, code-point U+00b5 can be entered as either ⌥ Opt+m or ⌥ Opt+Y.
Some information derived from the following web page:
Metric prefix - Wikipedia.
Units
International System of Units
What it measures | Name of Unit | Symbol |
---|---|---|
second | second | s |
length | meter | m |
mass | kilogram | kg |
electric current | ampere | A |
thermodynamic temperature | kelvin | K |
luminous intesity | candela | cd |
amount of substance | mole | mol |
The National Institute of Standards and Technology (NIST) has this graphic to explain units in greater detail.
Click here to visit the NIST Metric and SI Webpage
Putting it all together
Examples:
Numeric Value | Prefix | Unit of Measure | Expression |
---|---|---|---|
10 | kilo | meter | 10km |
0.1 | micro | ampere | 0.1µA |
Conversions:
Sometimes a number will not be easy to write or look correct unless it is converted up or down the scale.
Examples:
Starting Value | Number of positions to move. | Ending Value |
---|---|---|
1km | 3 | 1000m |
0.1µA | 6 | 100,000pA |