How to Calculate MG/KG/DAY

Milligrams per kilogram per day (mg/kg/day) is a simple way to calculate medication dosages for yourself or your patient. Follow these steps for calculating an accurate medication dosage.

Determine your weight or your patient's weight in kilograms. This is done by dividing weight in pounds by 2.2. For example, if a person weighs 110 pounds, divide 110 by 2.2, which equals 50 kilograms (110/2.2 = 50). This is done because one kilogram is equal to 2.2 pounds.

Next, multiply milligrams by kilograms. For example, if a medication is recommended to be dosed at 100 mg/kg/day and the patient weighs 50kg: 100mg x 50kg = 5,000mg/day.

Here is a complete example: Your patient weighs 55lb. You have a drug order for 10mg/kg/day. First, divide 55lb by 2.2kg. This equals 25kg. You will then multiply 10mg x 25kg to equal 250mg. You will give your patient 250mg per day.


Never use a zero after a terminal decimal point. This can lead to serious dosage errors. For example, 2 not 2.0 Always use a zero before a decimal point to prevent dosage errors. For example, 0.2 not .2


Think through your drug dosage. If it sounds like too much, it probably is. Question any dosage that doesn't make sense!