Calculation of Dosage & Metric
System
Kaleem ul Haq

Percentage Solutions
• Percentage w/w express the number of grams
of active substance in 100g of solution .
• Percentage w/v express the number of grams
of active substance in 100ml of solution.
• Percentage v/w express the number of ml of
active substance in 100g of solution .
• Percentage v/v express the number of ml of
active substance in 100ml of solution.

Percentage strength to millimoles Per
Liter
• Let C=Percentage w/v strength of a salt.
• W=milligrams of salt containing 1 millimole of
the specified ion
• 100 milliliter of solution contain C grams of
salt
• 1L of solution contain 10x C grams of
salt=10,000C milligrams
• Millimoles per liter = 10,000C/w

Calculation of doses
• We have following formulas for calculation of
doses
• Young’s Formula
• Dilling’s Formula
• Cowling’s Formula
• Fried’s Formula
• Bastedo’s formula
• Clark’s Formula
• Gaubin’s formula

• Young’s Formula :• Dose for Child = Age (years )/Age +12 x Adult
dose
• This formula is used for children under 12 years
of age
• Dilling’s Formula :• Dose for Child = Age (years)/20 x adult dose
• The fraction age/20 approx close to weight curve
between the ages 4 -20 so more than 10 years of
age

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Cowling’s formula :Dose of child = Age (Years )+1/ 24 x Adult dose
Fried’s formula :Dose of child = Age(months)/150 x Adult dose
Bastedo’s formula :Dose of child = Age (years )+3/30 x Adult dose
Clark’s formula :Dose of child = weight (pounds )/150 x Adult
dose

Gaubin’s formula
Age(years)
Dose for children with respect to adult
dose
under 1
1/12
1-2
1/8
2-3
1/6
3-4
1/4
4-7
1/3
7-14
1/2
14-20
2/3
21- 60
full adult dose
60-70
4/5
70-80
3/4
over 90
1/2

Square Meter Surface Area Method
• Child dose = Body Surface area of child x Adult dose
Body Surface area of child
• The average body surface area for an adult has been
given as 1.73meter square .

Reduction & Enlargement of Recipe
• The following rules are used in converting the
recipe from one system to another
• Rule 1 :• To convert the recipe in imperial system to
metric system
• Write grams in place of grains
• Divide the minims by 1.1 and write result in
millimeters (for small scale )
• Write grams in in place of ounce & milliliters
in place of fluidounce (for large scale)

• Rule 2 :• To convert a recipe in metric system to
imperial system
• Write grains in place of grams
• Multiply the milliliter by 1.1 and write the
result in in minims (small scale )
• Write ounce in place of grams & fluid ounce in
place of milliliters .

Calculation by Alligation
• Simple arithmetical method for calculation of
resulting strength after mixing solutions or
other substances .

Metric System
• The use of metric system of weights and
measures was legalized in 1897 by the weights
and measures (Metric System ) .

Length
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Basic unit = 1 meter (m)
1 decimeter (dm) = 1/10th part of 1 meter
1 centimeter (cm) = 1/100th part of 1 meter
1 millimeter (mm) = 1/1000th part of 1 meter
1 micrometer (um) = 1/1000th part of 1 cm
1 nanometer (nm) = 1/1000th path of 1micron`

Mass
• The international kilogram is the weight in
vacuum of platinum- iridium cylinder
preserved at the international Bureau of
Weights and Measurers
• Basic unit = 1 kilogram (kg)
• 1 gram (g) = 1/1000th part of a kg
• 1 milligram (mg) = 1/1000 part of a gram
• 1 micrograms (ug) = 1/1000 part of milligram

Capacity
• The 1 Liter is the volume occupied by a cube
with side of 1 decimeter
• Basic unit = 1 liter
• 1 milliliter = 1/1000th part of a liter
• 1 ml is equal to 1 cubic centimeter.