Units of Measure


 

Measuring Devices:

Graduated Cylinder

The Metric System

Length:

  • 1000 millimeters = 1 meter
  • 100 centimeters = 1 meter
  • 1000 meters = 1 kilometer

Mass (or weight):

  • 1000 milligrams = 1 gram
  • 1000 grams = 1 kilogram
  • 1000 kilograms = 1 metric ton

Volume:

  • 1000 milliliters = l liter
  • 1000 liters = 1 cubic meter

Area:

  • 10 000 square meters = 1 hectare
  • 100 hectares = 1 square kilometer

Prefixes:

  • micro means 1/1 000 000
  • milli- means 1/1000
  • centi- means 1/100
  • kilo- means 1000
  • mega- means 1 000 000

Symbols:

  • m for meter
  • mm for millimeter
  • cm for centimeter
  • km for kilometer
  • g for gram
  • mg for milligram
  • kg for kilogram
  • L for liter
  • mL for milliliter
  • m2 for square meter
  • m3 for cubic meter
  • km2 for square kilometer
  • t for metric ton
  • ha for hectare

Some special relationships:

  • 1 milliliter = 1 cubic centimeter
  • 1 milliliter of water has a mass of approximately 1 gram
  • 1 liter of water has a mass of approximately 1 kilogram
  • 1 cubic meter of water has a mass of approximately 1 metric ton

Legal/official (exact) definitions of inch-pound units as set by U.S. law:

  • 1 inch = 25.4 millimeters
  • 1 pound = 453.592 37 grams
  • 1 gallon = 3.785 411 784 liters

Note: In Canada the inch and the pound are defined identically, but 1 Canadian gallon = 4.546 09 liters.

Approximate conversion factors between inch-pound units and the International System of Units (SI):

  • Multiply inches by 2.54 to get centimeters (this conversion factor is exact)
  • Multiply feet by 0.305 to get meters
  • Multiply miles by 1.6 to get kilometers
  • Divide pounds by 2.2 to get kilograms
  • Multiply ounces by 28 to get grams
  • Multiply fluid ounces by 30 to get milliliters
  • Multiply gallons by 3.8 to get liters

 

One of the principal advantages of the Metric System is its use of only one unit (standard of size) for each parameter (thing that is being measured). The metric units are interrelated in such a way that only five fundamental standards are necessary. These fundamental standards are identified with an * in the tables below.

MECHANICS
Parameter: Metric Unit English Units
time
duration, delay
second *
s
second, minute
hour, day
frequency hertz
1/s
cycle per second
length
distance, displacement
meter
1/299 792 458 light sec
m
inch, foot, yard
rod, chain, furlong, mile
velocity, speed
rate of change of position
meter per second
m/s
foot per second
mile per hour, knot
acceleration
rate of change of velocity
meter per second squared
m/s2
foot per second squared
mass
quantity of material
gram *
g
ounce, pound, ton
force
push, pull, or weight
newton
kg m/s2
pound-force
impulse
force times time
newton second
kg m/s
pound-force second
momentum
mass times velocity
kilogram meter per second
kg m/s
pound foot per second
work, energy
force times distance
joule (pronounced "jewel")
= one newton meter
kg m2/s2
foot pound-force
power
rate of doing work
watt
= one joule per second
kg m2/s3
foot pound-force per second
horsepower
area
size of a surface
square meter
m2
square foot, square yard
acre, square mile
pressure
force per unit area
pascal
newton per square meter
kg/m s2
pound-force per square inch
volume, capacity cubic meter (stere)
m3
pint, quart, gallon
cubic foot, cubic yard
density, heaviness grams per cubic centimeter
g/cm3
pounds per cubic foot

 


HEAT
Parameter: Metric Heat Unit English Heat Unit
heat energy joule, calorie, Calorie
1 cal = 4.186 joules
1 Cal = 4186 joules
British Thermal Unit
temperature change kelvin * Fahrenheit degree
temperature degrees kelvin degrees Fahrenheit

 


LIGHT
Parameter: Metric Light Unit
luminous intensity candle *
luminous flux lumen
one candle produces 4 pi lumens
illumination lux
lumen per square meter
focus diopter
reciprocal meters
astronomical distance parsec

ELECTRICITY & MAGNETISM (There are no English electrical units)
Parameter: Metric Electrical Unit
electric charge coulomb *
96,500 coul = 1 faraday
faraday = 1 mole of electrons
electromotive force (EMF) volt (joule per coulomb)
capacitance farad (coulomb per volt)
electric current ampere (coulomb per second)
electric energy joule (watt second)
(newton meter)
KWH = 3,600,000 joules
electric power watt (joule per second)
electrical resistance ohm
(volt per ampere)
electrical conductivity siemens (coulomb per joule)
(ampere per volt)
electrical field strength volts per meter
electromagnetic inductance henry (pl. henrys)
magnetic field intensity oersted (formerly the gauss)
magnetic flux weber (108 maxwells)
magnetic flux density tesla
weber per square meter
magnetomotive force gilbert