Metric Numbers
(See also Metric/Imperial Conversion Charts and Unit Converter)
What is kilo, mega, giga, tera ... ?
In the Metric System there are standard ways to talk about big and small numbers:
- "kilo" for a thousand,
- "mega" for a million,
- and more ...
Example: A long rope measures one thousand meters
It is easier to say it is 1 kilometer long,
and even easier to write it down as 1 km.
So we used kilo in front of the word meter to make "kilometer".
And the abbreviation is "km" (k for kilo and m for meter, put together).
Some more examples:
Example: You put your bag on a set of scales and it shows 2000 grams, we can call that 2 kilograms, or simply 2 kg.
Example: Teaspoon
A teaspoon holds 5 thousandths of a liter (\frac{5}{1000} of a liter), but it is better to say "5 milliliters", or write it simply as 5 mL.
"kilo", "mega", "milli" etc are called "prefixes":
Prefix: a word part that can be added to the beginning of another word to create a new word
So, using the prefix "milli" in front of "liter" creates a new word "milliliter".
Here we list the prefix for commonly used big and small numbers:
Common Big and Small Numbers
Name | The Number | Prefix | Symbol |
trillion | 1,000,000,000,000 | tera | T |
billion | 1,000,000,000 | giga | G |
million | 1,000,000 | mega | M |
thousand | 1,000 | kilo | k |
hundred | 100 | hecto | h |
ten | 10 | deka | da |
unit | 1 | ||
tenth | 0.1 | deci | d |
hundredth | 0.01 | centi | c |
thousandth | 0.001 | milli | m |
millionth | 0.000 001 | micro | µ |
billionth | 0.000 000 001 | nano | n |
trillionth | 0.000 000 000 001 | pico | p |
Just remember for large values (each one a thousand times bigger):
"kilo mega giga tera"
and for small values (each one a thousand times smaller):
"milli micro nano pico"
Try To Do Some Yourself!
- How do you refer to a million liters?
- How about one billionth of a meter?
See the bottom of this page for more questions to challenge yourself ...
How Big Are They?
There is a lot of difference between them. Think in terms of time:
A billion seconds is about 32 years
A longer list:
- A thousand seconds is about a quarter of an hour
- A million seconds is about 12 days
- A billion seconds is about 32 years, almost half a lifetime
- A trillion seconds is about 32,000 years (the last Ice Age finished 12,000 years ago)
Much Bigger and Smaller
There are also prefixes for much bigger and smaller numbers:
Some Very Big, and Very Small Numbers
Name | The Number | Prefix | Symbol |
Very Big ! | |||
septillion | 1,000,000,000,000,000,000,000,000 | yotta | Y |
sextillion | 1,000,000,000,000,000,000,000 | zetta | Z |
quintillion | 1,000,000,000,000,000,000 | exa | E |
quadrillion | 1,000,000,000,000,000 | peta | P |
Very Small ! | |||
quadrillionth | 0.000 000 000 000 001 | femto | f |
quintillionth | 0.000 000 000 000 000 001 | atto | a |
sextillionth | 0.000 000 000 000 000 000 001 | zepto | z |
septillionth | 0.000 000 000 000 000 000 000 001 | yocto | y |
Also see Lengths From Very Small to Very Large |
All Big Numbers We Know
Name | As a Power of 10 | As a Decimal |
Thousand | 10^{3} | 1,000 |
Million | 10^{6} | 1,000,000 |
Billion | 10^{9} | 1,000,000,000 |
Trillion | 10^{12} | 1,000,000,000,000 |
Quadrillion | 10^{15} | etc ... |
Quintillion | 10^{18} | |
Sextillion | 10^{21} | |
Septillion | 10^{24} | |
Octillion | 10^{27} | |
Nonillion | 10^{30} | |
Decillion | 10^{33} | |
Undecillion | 10^{36} | |
Duodecillion | 10^{39} | |
Tredecillion | 10^{42} | |
Quattuordecillion | 10^{45} | |
Quindecillion | 10^{48} | |
Sexdecillion | 10^{51} | |
Septemdecillion | 10^{54} | |
Octodecillion | 10^{57} | |
Novemdecillion | 10^{60} | |
Vigintillion | 10^{63} | 1 followed by 63 zeros! |
And a Googol is 1 followed by one hundred zeros (10^{100}) :
10,000,000,000,000,000,000,000,000,000,000,000,
000,000,000,000,000,000,000,000,000,000,000,
000,000,000,000,000,000,000,000,000,000,000
Then there is the Googolplex. It is 1 followed by Googol zeros. I can't even write down the number, because there is not enough matter in the universe to form all the zeros:
10,000,000,000,000,000,000,000,000,000,000, ... (Googol number of Zeros)
And a Googolplexian is a 1 followed by Googolplex zeros. Wow.
All Small Numbers We Know
Name | As a Power of 10 | As a Decimal |
thousandths | 10^{-3} | 0.001 |
millionths | 10^{-6} | 0.000 001 |
billionths | 10^{-9} | 0.000 000 001 |
trillionths | 10^{-12} | etc ... |
quadrillionths | 10^{-15} | |
quintillionths | 10^{-18} | |
sextillionths | 10^{-21} | |
septillionths | 10^{-24} | |
octillionths | 10^{-27} | |
nonillionths | 10^{-30} | |
decillionths | 10^{-33} | |
undecillionths | 10^{-36} | |
duodecillionths | 10^{-39} | |
tredecillionths | 10^{-42} | |
quattuordecillionths | 10^{-45} | |
quindecillionths | 10^{-48} | |
sexdecillionths | 10^{-51} | |
septemdecillionths | 10^{-54} | |
octodecillionths | 10^{-57} | |
novemdecillionths | 10^{-60} | |
vigintillionths | 10^{-63} |