How to Calculate the Amount of a Dose Depending on Weight

Medications are sometimes prescribed in doses depending on the weight of the patient. Most pills are measured by the metric system, in fractions of a gram. To calculate dosage based on this system, you must know your weight in kilograms. If you know your weight in pounds but not kilograms, you must convert it. Then, simple calculations will show what the dosage should be, and how many pills you should take.

Things You'll Need

• Calculator

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Instructions

Your Weight in Kilograms

• 1

  Divide your weight in pounds by 2.2. There are 2.2 pounds in a kilogram, so the answer is your weight in kilograms. For example, a 45 pound child would weigh 20.45kg, and a 165 pound adult would weigh 75kg.

• 2

  Make sure the label on your medication gives the amount in each pill. This will usually be in milligrams, though it may be in smaller increments, such as micrograms. If the amount is not on the label, ask your pharmacist to correct the label. The label should also define the amount of medicine to be taken, such as 2mg per kilogram, twice a day.

• 3

  Calculate the dosage by multiplying the weight in kilograms by the prescribed dosage. If the 20.45kg child is prescribed 2mg per kg, the dosage would be 41mg. The 75kg adult would require 150 mg (75 x 2) for the same prescription.

• 4

  Compare the dosage required with the content of the pill. If the child has 20mg pills, he would need two pills. If the adult has 50mg pills, she would need three pills.

• 5

  Double-check your calculations and compare with the doctor's instructions on the label of the medicine. Check with the pharmacist if there is any problem. Otherwise, begin taking the medicine and continue taking as prescribed.