The
Metric
System
Ms. Ryan
MCATC
Medical Math
2015-2016
2
Basic Units of Metric Measurement
3
Understanding Metric Notation
 Metric
system is based on multiples of 10.
 Prefix before the basic unit indicates size.
 Kilo – indicates you multiply the basic unit
by 1000.
 Kilometer
– 1000 meters
 Kilogram – 1000 grams
 Kiloliter – 1000 liters
4
Understanding Metric Notation
 Prefix
milli- means one-thousandth.
 Millimeter is one-thousandth of a meter.
 Milliliter is one-thousandth of a liter.
 Milligram is one-thousandth of a gram.
Chapter 3
Convert Larger to Smaller






2 L = ?? mL
mL = 0.001
Move the decimal to the right 3 places
2.0 L = 2000 mL
OR multiply
2 X 1000 = 2000
Convert Smaller to Larger
 250
mg = ?? g
 milli = 0.001 so move the decimal point 3
places to the left
 250 mg = 0.250 g (drop the trailing zero)
 OR divide 250 ÷ 1000 = 0.250
Metric System
RULES

Do not use a period with the
abbreviation of metric units
 May be mistaken for another letter or
symbol

1)
2)
mg
ml

1)
2)
Correct:
mg.
ml.
Incorrect:
Metric System
RULES

Use Arabic numerals to
express the quantity of
the dose
 Correct:
4 mg
 Incorrect: IV mg
10
Metric System
RULES
 Meter
and gram are abbreviated with
lowercase letters.
 Liter is abbreviated with an uppercase L.
 This minimizes the chance of confusion
between 1 and the lowercase l.
11
Metric System
RULES
 Write

fractions as decimals
Example: Write 1.25 g to represent 1 1/4 g
 If
the quantity is less than 1, include a 0 before the
decimal point.

Example: Do not write .750
write 0.75
 No
trailing zeros: 0.750 is written as 0.75
12
Metric System
RULES
Write the unit after the quantity with a space
between them.

Example: Write 30 mg
not mg 30
13
Example for Practice

Consider the previous rules to
determine the correct metric
notation for six and two-eighths
milliliters.
a.
b.
c.
d.
6.28mL
ml 6.25
6 14 mL
6.25 mL
Chapter 3
Answer d. 6.25 mL
14
REMEMBER
Converting within the Metric
System
To convert a quantity from one unit
of metric measurement to
another:
1. Move the decimal point to the right if you are
converting from a larger unit to a smaller unit.
2. Move the decimal point to the left if you are
converting from a smaller unit to a larger unit.
15
Examples for Practice
1. Convert 4 L to mL.
2. How many m are in 75 mm?
16
Error Alert!
Remember:
The larger the unit,
the smaller the quantity. The
smaller the unit, the larger the
quantity.


Example: 1 dollar bill = 4 quarters = 100 pennies
Example: 100 pennies = 4 quarters = 1 dollar bill