## The Metric System

The metric system is an international "decimalised" system of measurement that was originally based on the mètre des archives and the kilogramme des archives introduced by France in 1799. Over the years, the definitions of the metre and kilogram have been refined and the metric system extended to incorporate many more units. Although a number of variants of the metric system emerged in the late nineteenth and early twentieth centuries the term is now often used as a synonym for the "International System of Units" - the official system of measurement in almost every country in the world.

## Decimals in Measurement

Length

The standard unit of length in the metric system is the meter. Other units of length and their equivalents in meters are as follows:

1 millimeter = 0.001 meter

1 centimeter = 0.01 meter

1 decimeter = 0.1 meter

1 kilometer = 1000 meters

We symbolize these lengths as follows:

1 millimeter = 1

Volume

The standard unit of volume in the metric system is the liter. One liter is equal to 1000 cubic centimeters in volume. Other units of volume and their equivalents in liters are as follows:

1 milliliter = 0.001 liter

1 centiliter = 0.01 liter

1 deciliter = 0.1 liter

1 kiloliter = 1000 liters

From these units, we see that 1000 milliliters equal 1 liter; so 1 milliliter equals 1 cubic centimeter in volume. We symbolize these volumes as follows:

1 milliliter = 1

Mass

The standard unit of mass in the metric system is the gram. Other units of mass and their equivalents in grams are as follows:

1 milligram = 0.001 gram

1 centigram = 0.01 gram

1 decigram = 0.1 gram

1 kilogram = 1000 grams

We symbolize these masses as follows:

1 milligram = 1

Time

The following conversions are useful when working with time:

1 minute = 60 seconds

1 hour = 60 minutes = 3600 seconds

1 day = 24 hours

1 week = 7 days

1 year = 365 1/4 days (for the Earth to travel once around the sun)

In practice, every three calendar years will have 365 days, and every fourth year is a "leap year", which has 366 days, to make up for the extra quarter day over four years. The years 1992, 1996, 2000, and 2004 are all leap years. This gives us a total of 52 complete 7 day weeks in each calendar year, with 1 day left over (or 2 in a leap year).

The year is divided into 12 months, each of which has 30 or 31 days, except for February, which has 28 days (or 29 days in a leap year).

The standard unit of length in the metric system is the meter. Other units of length and their equivalents in meters are as follows:

1 millimeter = 0.001 meter

1 centimeter = 0.01 meter

1 decimeter = 0.1 meter

1 kilometer = 1000 meters

We symbolize these lengths as follows:

1 millimeter = 1

*mm*

1 centimeter = 1*cm*

1 meter = 1*m*

1 decimeter = 1*dm*

1 kilometer = 1*km*Volume

The standard unit of volume in the metric system is the liter. One liter is equal to 1000 cubic centimeters in volume. Other units of volume and their equivalents in liters are as follows:

1 milliliter = 0.001 liter

1 centiliter = 0.01 liter

1 deciliter = 0.1 liter

1 kiloliter = 1000 liters

From these units, we see that 1000 milliliters equal 1 liter; so 1 milliliter equals 1 cubic centimeter in volume. We symbolize these volumes as follows:

1 milliliter = 1

*ml*

1 centiliter = 1*cl*

1 deciliter = 1*dl*

1 liter = 1*l*

1 kiloliter = 1*kl*Mass

The standard unit of mass in the metric system is the gram. Other units of mass and their equivalents in grams are as follows:

1 milligram = 0.001 gram

1 centigram = 0.01 gram

1 decigram = 0.1 gram

1 kilogram = 1000 grams

We symbolize these masses as follows:

1 milligram = 1

*mg*

1 centigram = 1*cg*

1 decigram = 1*dg*

1 gram = 1*g*

1 kilogram = 1*kg*Time

The following conversions are useful when working with time:

1 minute = 60 seconds

1 hour = 60 minutes = 3600 seconds

1 day = 24 hours

1 week = 7 days

1 year = 365 1/4 days (for the Earth to travel once around the sun)

In practice, every three calendar years will have 365 days, and every fourth year is a "leap year", which has 366 days, to make up for the extra quarter day over four years. The years 1992, 1996, 2000, and 2004 are all leap years. This gives us a total of 52 complete 7 day weeks in each calendar year, with 1 day left over (or 2 in a leap year).

The year is divided into 12 months, each of which has 30 or 31 days, except for February, which has 28 days (or 29 days in a leap year).

## Sample Exercise

Convert the following.

1000 mg = _______g

160 cm = _______mm

1 L = _______mL

250 m = _______km

109 g = _______kg

Check your answers here.

1000 mg = _______g

160 cm = _______mm

1 L = _______mL

250 m = _______km

109 g = _______kg

Check your answers here.