SI
prefixes
The 20
SI prefixes used to form decimal multiples and submultiples of SI units
are given in Table 5.
Table 5. SI prefixes
|
Factor |
Name |
Symbol |
1024 |
yotta |
Y |
1021 |
zetta |
Z |
1018 |
exa |
E |
1015 |
peta |
P |
1012 |
tera |
T |
109 |
giga |
G |
106 |
mega |
M |
103 |
kilo |
k |
102 |
hecto |
h |
101 |
deka |
da | |
|
Factor |
Name |
Symbol |
10-1 |
deci |
d |
10-2 |
centi |
c |
10-3 |
milli |
m |
10-6 |
micro |
µ |
10-9 |
nano |
n |
10-12 |
pico |
p |
10-15 |
femto |
f |
10-18 |
atto |
a |
10-21 |
zepto |
z |
10-24 |
yocto |
y | |
|
It is
important to note that the kilogram is the only SI unit with a prefix as
part of its name and symbol. Because multiple prefixes may not be used, in
the case of the kilogram the prefix names of Table 5 are used with
the unit name "gram" and the prefix symbols are used with the unit symbol
"g." With this exception, any SI prefix may be used with any SI unit,
including the degree Celsius and its symbol °C.
Example
1: |
10-6
kg = 1 mg (one milligram), but not
10-6 kg = 1 µkg (one microkilogram) |
Example
2: |
Consider
the earlier example of the height of the Washington Monument. We may
write hW = 169 000 mm = 16 900
cm = 169 m = 0.169 km using the millimeter (SI prefix milli,
symbol m), centimeter (SI prefix centi, symbol c), or kilometer (SI
prefix kilo, symbol k). |
Because
the SI prefixes strictly represent powers of 10, they should not be used
to represent powers of 2. Thus, one kilobit, or 1 kbit, is 1000 bit and
not 210 bit = 1024 bit. To alleviate this
ambiguity, prefixes for binary
multiples have been adopted by the International Electrotechnical
Commission (IEC) for use in information technology.
Continue to Units
outside the SI
|