MEASUREMENT

Glossary of Mathematics | Measurement | Areas and Volumes

SI UNITS

A system of coherent metric units proposed for international acceptance in 1960 and now recognised world wide.  It comprises 7 base and 2 supplementary units.

UNIT
SYMBOL
QUANTITY
metre m Length
kilogramme kg Mass
second s Time
ampere A Current
kelvin K Temperature
candela cd Luminous intensity
mole mol Relativemolecular mass
radian rad Plain angles
steradian sr Solid angles

The 9 SI Units can be combined to form derived units. for example, the unit of force (Newtons) is derived thus: kg m s-2 . Each unit can be prefixed with a further symbol or index to indicate the magnitude of the unit.  So for example:  1000m = 1 x 103  =1km

SI PREFIXES

SYMBOL
NAME
VALUE
G giga 109 1 000 000 000
M mega 106 1 000 000
k kilo 103 1 000
h hecto 102 100
da deca 101 10
d deci 10-1 0.1
c centi 10-2 0.01
m milli 10-3 0.001
µ micro 10-6 0.000 001
n nano 10-9 0.000 000 001

CONVERSION FACTORS

MULTIPLY
BY
TO GET
LENGTH
millimetres 0.039 inches
metres 3.28 feet
metres 1.0936 yards
kilometres 0.621 miles
inches 25.4 millimetres
feet 304.8 millimetres
yards 0.914 metres
miles 1.609 kilometres
AREA
metres²  1.196  yards²
feet²  0.093  metres²
yards²  0.836 metres²
yards²  4 840 acre
miles²  640 acres
VOLUME
centimetre³  0.061  inches³
metres³  1.308  yards³
metres³  35.315  feet³
inches³  6.452  centimetre³
feet³  0.028  metres³
yards³  0.836  metres³
SPEED
miles/hour 1.609  kilometres/hour
kilometres/hour  0.621  miles/hour
MASS
grammes  0.035  ounces
kilograms  2.205  pounds
tonnes  0.984 tons
ounces  28.350 grammes
pounds  0.454  kilograms
tons 1.016 tonnes
CAPACITY
gallons  4.546 litres
litres  0.220  gallons
PRESSURE
pounds/inch²  0.0689  bar
bar 14.5  pounds/inch²
ENERGY
horsepower  0.7457 kilowatts
kilowatts  1.341 horsepower

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