Biology 12

2

APPENDIX

552 MHR • Appendix 2

When you take measurements in science, you

use the International System of Measurement

(commonly known as SI, from the French

Système international d’unités). SI includes the

metric system and other standard units. It is

accepted as the standard for measurement

throughout most of the world. This appendix

provides you with a review of SI metric

symbols and prefixes.

In SI, the base units include the metre, the

kilogram, and the second. The size of any

particular unit can be determined by the prefix

used with the base unit. Larger and smaller

units of measurement can be obtained by either

dividing or multiplying the base unit by a

multiple of 10.

For example, the prefix kilo-means

multiplied by 1000. So, one kilogram is

equivalent to 1000 grams:

1 kg=1000 g

The prefix milli-means divided by 1000. So,

one milligram is equivalent to one thousandth

of a gram:

1 mg= 10001 g

The following table shows the most

commonly used metric prefixes. Adding metric

prefixes to a base unit is a way of expressing

powers of 10.

* Many dieticians in North America continue

to measure nutritional energy in Calories,

also known as kilocalories or dietetic

Calories. In SI units, 1 Calorie =4.186 kJ.

** In current North American medical

practice, blood pressure is measured in

millimetres of mercury, symbol mm Hg.

In SI units, 1 mm Hg =0.133 kPa.

Quantity Unit Symbol

length

mass

area

volume

time

temperature

force

energy

pressure

electric current

quantity of electric charge

frequency

power

nanometre

micrometre

millimetre

centimetre

metre

kilometre

gram

kilogram

tonne

square metre

square centimetre

hectare

cubic centimetre

cubic metre

millilitre

litre

second

degree Celsius

newton

joule

kilojoule *

pascal

kilopascal **

ampere

coulomb

hertz

watt

nm

μm

mm

cm

m

km

g

kg

t

ha (10 000 )

mL

L

s

̊C

N

J

kJ

Pa

kPa

A

C

Hz

W

Commonly Used Metric Quantities, Units, and Symbols

m^2

cm^2

m^2

m^3

cm^3

Prefix Symbol Relationship to the base unit

giga-

mega-

kilo-

hecto-

deca-

• deci-
  centi-
  milli-
  micro-
  nano-

G

M

k

h

da

• d c m μ n

Metric Prefixes

109 =1 000 000 000

106 =1 000 000

103 =1 000

102 = 100

101 = 10

100 = 1

10 −^1 =0.1

10 −^2 =0.01

10 −^3 =0.001

10 −^6 =0.000 001

10 −^9 =0.000 000 001

Units of Measurement