Metric System Basics

Why we need International Standardization

The issue of standards hose couplings was eventually settled in the early 1930's, at least in the United States – however, it appears that even today, fire trucks in many areas around Baltimore still carry adapters to hook two different types of fire hydrants to their hoses…….

Three competing screw and fastener standards existed

- British Whitworth Standards- American "Sellers" Standards- Baltimore Steamer Standards...and c. 600 other!

Hose couplings could not attach to the hydrants or to other hoses

Baltimore fire – 1904

At the international level the international screw thread debate in ISO – started in 1947 with the creation of

ISO TC 1 "Screw Threads" and – went on in earnest for some 17 years

before the first standard was published, and

– continued another 20 years before the definitive set of metric ISO screw thread standards were finally approved in the early 1980's

Screw Threads

• Pre-1791 - many units were based on (Royal) body parts (e.g. the King’s foot)

• 1791 - Metric system introduced (in France, at the height of the Revolution)

• 1840 - Metric system obligatory in France

• 1875 - ‘Metre Convention’ signed by 17 nations

• 1960 - SI Units system (Système International d’Unités) established (in Paris)

• 1978 - ISO 31 (SI Units) published

• 2006 - USA, Myanmar (Burma), and Liberia officially remain non-metric countries

International standards are essential

SI UnitsA 200+ year-old base for trade …

metre (m)

kilogram (kg)

second (s)

ampere (A)

kelvin (K)

mole (mol)

candela (cd)

• Oil trades internationally as ‘barrels’, a non-metric quantity standardized in 1872 as 42 US Gallons

• Reference to US Gallon is vital even if it is not an SI/metric unit because the defining pint sub-unit is different

– USA gallon (8 USA pints) = 3.785411784 Litres

– UK gallon (8 UK pints ) = 4.54609 Litres

That is a difference of 32 litres compared with the same (larger) quantity expressed in UK gallons!

International standards are essentialSelling oil in ‘barrels:’

A standardized exception to the rules

• 17c - Measures existed (broc, sétier, pot, pichet, etc.) but varied between towns

• 1616 – Berne attempted to impose standards• 1791 – Metric system being developed in France• 1801 – First Swiss uniform system of measures • 1822 – Swiss Pot was standardized as 1.35 l• 1836 – Swiss Pot revised to 1.5 l with Demi-pot of

0.75 l• 1877 – Full metric system adopted across

Switzerland• Now – Eurobottle of 0.75 l has been adopted world-

wide

International standards are essentialA Swiss case (of wine) …

(From serving aid to measure to standard)

7

Thomas Jefferson was intrigued by the metric

system and strongly advocated the use of

decimal-based measures

But he only got half of what

he wanted...

8

METRIC MONEY

That is, money based on the decimal system

9

….and “metric”stock prices, too

That is, decimal-basedstock prices

10

BUT we insist on keeping the archaic

inch-poundmeasurement system

based on...

11

fractions of an inch...12 inches to a foot….

3 feet to a yard…. 5.5 yards to a rod...320 rods to a mile...

43,560 sq ft to an acre...

12

16 ounces to a pound...(avoirdupois)

12 ounces to a pound...(troy)

4 quarts to a gallon...3 teaspoons to a

tablespoon…

13

You get the point

Metric System• The metric system is based on a base

unit that corresponds to a certain kind of measurement

• Length = meter• Volume = liter• Weight (Mass) = gram

• Prefixes plus base units make up the metric system – Example:

• Centi + meter = Centimeter• Kilo + liter = Kiloliter

Metric System• The three prefixes that we will use

the most are:– kilo– centi– milli

kilo hecto deca

Base Units

metergramliter

deci centi milli

Metric System• So if you needed to measure

length you would choose meter as your base unit– Length of a tree branch

• 1.5 meters

– Length of a room • 5 meters

– Length of a ball of twine stretched out• 25 meters

Metric System• But what if you need to measure a

longer distance, like from your house to school?– Let’s say you live approximately 10

miles from school• 10 miles = 16093 meters

– 16093 is a big number, but what if you could add a prefix onto the base unit to make it easier to manage:• 16093 meters = 16.093 kilometers (or

16.1 if rounded to 1 decimal place)

Metric System• These prefixes are based on powers of

10. What does this mean?– From each prefix every “step” is either:

• 10 times larger or

• 10 times smaller

– For example• Centimeters are 10 times larger than millimeters• 1 centimeter = 10 millimeters

kilo hecto deca

Base Units

metergramliter

deci centi milli

Metric System

– Centimeters are 10 times larger than millimeters so it takes more millimeters for the same length

1 centimeter = 10 millimetersExample not to scale

1 mm

1 mm

1 mm

1 mm

1 mm

1 mm

1 mm

1 mm

1 mm

1 mm

1 cm

40

41

41

40

Metric System• For each “step” to right,

you are multiplying by 10

• For example, let’s go from a base unit to centi

1 liter = 10 deciliters = 100 centiliters

2 grams = 20 decigrams = 200 centigrams

kilo hecto deca

meterliter

gram

deci centi milli

( 1 x 10 = 10) = (10 x 10 = 100)

(2 x 10 = 20) = (20 x 10 = 200)

Metric System• An easy way to move within the metric

system is by moving the decimal point one place for each “step” desired

Example: change meters to centimeters

1 meter = 10 decimeters = 100 centimetersor

1.00 meter = 10.0 decimeters = 100. centimeters

kilo hecto deca

meterliter

gram

deci centi milli

Metric System• Now let’s try our previous example from

meters to kilometers:16093 meters = 1609.3 decameters =

160.93 hectometers = 16.093 kilometers

• So for every “step” from the base unit to kilo, we moved the decimal 1 place to the left (the same direction as in the diagram below)

kilo hecto deca

meterliter

gram

deci centi milli

Metric System• If you move to the left in the diagram,

move the decimal to the left

• If you move to the right in the diagram, move the decimal to the right

kilo hecto deca

meterliter

gram

deci centi milli

Metric System• Now let’s start from centimeters and

convert to kilometers

400000 centimeters = 4 kilometers

400000 centimeters = 4.00000 kilometers

kilo hecto deca

meterliter

gram

deci centi milli

Metric System• Now let’s start from meters and convert to

kilometers

4000 meters = 4 kilometers

kilo hecto deca

meterliter

gram

deci centi milli

kilo hecto deca

meterliter

gram

deci centi milli

• Now let’s start from centimeters and convert to meters

4000 centimeters = 40 meters

Metric System• Now let’s start from meters and convert to

centimeters

5 meters = 500 centimeters

kilo hecto deca

meterliter

gram

deci centi milli

kilo hecto deca

meterliter

gram

deci centi milli

• Now let’s start from kilometers and convert to meters

.3 kilometers = 300 meters

Metric System• Now let’s start from kilometers and convert to

millimeters

4 kilometers = 4000000 millimetersor

4 kilometers = 40 hectometers = 400 decameters = 4000 meters = 40000 decimeters = 400000 centimeters = 4000000

millimeters

kilo hecto deca

meterliter

gram

deci centi milli

Metric System• Summary

– Base units in the metric system are meter, liter, gram

– Metric system is based on powers of 10– For conversions within the metric system, each

“step” is 1 decimal place to the right or left– Using the diagram below, converting to the right,

moves the decimal to the right and vice versa

kilo hecto deca

meterliter

gram

deci centi milli

Temperature Conversion

• In the United States, temperature is measured and recorded in the Fahrenheit scale in everyday use.

• Many other countries measure temperature by using the Celsius(Centigrade) scale.

• Knowing the differences between the two scales and how to convert from one scale to the other is important to travelers.

The Fahrenheit and Celsius Scales

• The Fahrenheit scale is based on a scale of 32° (freezing point) and 212° (boiling point).

• The Celsius system is based on a scale of 0°C (freezing point) to 100° (boiling point).

Convert Between Celsius and Fahrenheit Temperatures

• To convert between Celsius (C) and Fahrenheit (F) temperatures, you can use one of these two formulas.

F = 1.8C + 32

C =

1.8

32F