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 mm
1 centimeter = 1 cm
1 meter = 1 m
1 decimeter = 1 dm
1 kilometer = 1 km
For reference, 1 meter is a little longer than 1 yard or 3 feet. It is about half
the height of a very tall adult. A centimeter is nearly the diameter of a dime,
a little less than half an inch. A millimeter is about the thickness of a dime.
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
For reference, 1 liter is a little more than 1 quart. One teaspoon equals about
5 milliliters.
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
For reference, 1 gram is about the mass of a paper clip. One kilogram is about
the mass of a liter of water.
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).
Temperature
Temperature is expressed in degrees Celsius in the metric system. The boiling
point of water (at sea level) is 100°Celsius, or 100°C. The freezing
point of water (at sea level) is 0° Celsius. A hot day is about 30° Celsius.
Decimals in measurement
We use decimals to specify units of measurement when we need more precision about
length, volume, mass, or time. For example, when specifying the height of a person
1.63 meters tall, to say that person is 1 or 2 meters tall doesn't give us a very
good idea of how tall that person really is.
The prefixes for the different units of length, volume, and mass in the metric system
obey the following rules:
| Prefix | Multiply by |
| milli- | 0.001 |
| centi- | 0.01 |
| deci- | 0.1 |
| deka- | 10 |
| hecto- | 100 |
| kilo- | 1000 |
So for example:
1 hectometer = 100 meters
1 centigram = 0.01 gram
3 milliliters = 3 × (0.001 liters) = 0.003 liters
0.9 kilometers = 0.9 × (1000 meters) = 900 meters
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