A beginners guide to the Metric System

Wednesday, December 30, 2015

How does the metric system work?

The metric system is used worldwide in order to measure length, mass, and volume time, current, and even luminosity.
The scientific community has adopted the metric system as its standard system of measurement.
In the United States, the metric system seems a little odd because the United States remains the only industrialized country that has not adopted the metric system as its official system of measurement.

united states does not use metric system

A major feature of the metric system is the use of a standard set of inter-related base units, and a standard set of prefixes based on the powers of ten.

  • This allows for easy conversion among units and insight into what is being measured.
  • For example, 100 meters can easily be converted to centimeters by moving the decimal one place to the right, and the prefix " meters " indicates you will be measuring length.

The base units of the metric system

The meter is the standard unit for length. For example, if you see 1000 kilometers, the meters at the end of the word indicates that the measurement is of length.
ruler representing distance in the metric system
A Liter is a unit for volume.

beaker representing volume

The Gram is a unit for mass.
weights representing mass in the metric system

Again, the standard unit indicates the type of measurement.
  • 12,234 kilograms will be a measurement of mass.
  • .056 milliliters are measuring volume.
  • 45 hectometers are measuring length
Since 1960 the metric system has been called the System of International Units and is abbreviated SI.

The SI has seven official units of measurement. Other units like the liter are accepted but are not official. Here is a chart of the 7 SI units of measurement.

Name           Measures                   Abbreviation

Meter            length                                m
Kilogram       mass                                 kg
Second          time                                   s

Kelvin           temperature                      K

Mole             amount of a                      mol.

Ampere         electric current                 A

Candela         luminous intensity           cd

The prefixes of the metric system

The metric system also uses prefixes in order to make conversion between different measurements easy and accurate. 

The most common metric prefixes from largest to smallest.
Prefix                                                      Power                           Factor

kilo                                                          10^3                              1000    

hecto                                                        10^2                              100

deka                                                         10^1                              10

base unit ( meter liter gram)                 

deci                                                         10^-1                              .1

centi                                                        10^-2                            .01

milli                                                         10^-3                            .001

These are not the only prefixes used in the metric system. These six prefixes are taught most often in elementary, middle, and high school in the United States. In fact, there are 24 prefixes in the metric system that range from the yotta ( 10^24) which is used for very large measurements, to the yocto (10^-24) which would measure incredibly small objects.However, for a beginners guide these seven prefixes are used most often.

An easy acronym for remember the metric prefixes is,

King     Henry   Died      By        Drinking  Chocolate  Milk  
kilo       hecto     deka      base     deci           centi          milli


Kangaroos    Have      Dirty     Underwear     During     Cold      Months
kilo                hecto       deka        unit                  deci          centi      milli

Why are the prefixes in the metric system important?

Communication: The prefixes allow people from all over the world to communicate about measurements. If someone in Japan sends an email to Europe and tells them the inseam of the dress equals 120 centimeters, both people can easily understand this distance. This allows people in many diverse fields to communicate easily about measurements.

Ease of Conversion

Because the metric system is based on factors of ten, conversion among the different size units can be quick and easy. Like many things in life, there is a learning curve to conversion. If we start at a kilometer and break it into 10 equal parts, then one of these equal parts is a hectometer. Subdivide the hectometer into 10 equal parts, and one of these parts is a dekameter. A meter divided into 10 equal parts produces 10 centimeters, and so forth. This allows you to convert among units by just moving a decimal point to the left or the right.

What does the meter, liter, and gram actually measure?

The standard for the meter originally was equal to one ten-millionth the distance between the North Pole and the Equator on a meridian that passes through Paris. This distance from the North Pole to the equator worked out to be one fourth the circumference of the Earth. Today it is the length of the path traveled by light in a vacuum during a time interval of 1/299 792 458 of a second.

liter is equal to the volume of one cubic decimeter. Put another way, a liter is the volume of a cube with sides of 10 centimeters. Technically a liter is not an official SI unit but is an accepted SI unit.
The official unit for volume is the cubic meter. (m^3)

gram is equal to the mass of one cubic centimeter of pure water at 39.2 degrees F ( 4 degrees C)
The official mass of a gram is 0.001 kilogram.

Why the metric system? 5 reasons why I like the metric system

1. To bring order to chaos. The metric system was devised in France in the 18th century. At the time there was a mixture of measurements and little organization. The goal of the metric system was to replace this disorganization with a system based on standard units and a decimal system.

2. The metric system is used universally. The international scientific community has mandated the use of the metric system, and the US is one of the few industrialized countries that has not adopted the metric system.

3. It is easy to use. Because it is based on powers of ten and has interrelated units it is easy to use. For example, compare the metric system to how I measure in Georgia. If I want to measure the distance I could measure the distance in inches, feet, yards, or miles. None of these units give any clue that they are measuring distance. If I use the metric system I could measure in centimeters, decimeters, millimeters, or kilometers. The term meter tells me it is measuring distance.

4. Less chance of mistakes. The use of decimals and powers of ten make calculations easier and reduce the chance of errors.

5. Calculations are faster. Compare converting from Meters to millimeters 5 meters = 5000 mm
I simply move the decimal three places to the left.
Now convert yards to inches. 5 yards = 5 x 3 in order to convert to feet, then 3 x 12 in order to convert to inches. = 180

Estimating with the metric system with common objects


Millimeter    The width of a pencil is about 6 millimeters

Centimeter   The width of your pinky

Meter            Distance from a doorknob to the floor

Kilometer     60 % of a mile. A 10K running race is 6.2 miles


Milliliter      A teaspoon is about 5 milliliters

Liter             A gallon of milk is almost 4 liters ( 3.78541 to be exact)


Gram          One nickel 5 grams

Gram          Can of  tomatoes is about 500 grams

Kilogram    Is roughly 2 pounds ( 2.20 pounds)

Kilogram     Average laptop  is about 2 kilograms

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