Dr. Saqib Khan

Paediatrics Dose Calculator

Pediatric dosage

Dosing estimates for children may be calculated in a number of ways, the most frequent of which are weight or surface area (BSA).

The dosage and delivery schedule may range from once daily to every hour, and the units of measure used are commonly milligrams per kilogram per day (mg/kg/day) or milligrams per kilogram per dose. You may also use mcg/kg/day or mcg/kg/dose in the above calculations to make things easier.

Paediatrics Dose Calculator

Calculation of Child doses

Based on weight

Due to the immaturity of their physiological systems (such as absorption, distribution, metabolism, and excretion), children are more likely to have adverse effects from medications, including overdose and death. Young newborns often have decreased metabolism and excretion due to impaired hepatic and renal function. When a teen weighs at least 50 kilograms (about 110 pounds), doctors may safely administer adult doses.

Children’s doses may be derived from adult doses by multiplying the child’s weight in kilograms by the dosage conversion factor. Noting whether the dosage is based on a daily dose or an administration dose is crucial.


  • Child dose by weight = (mg/dose) = Adult Dose in mg/kg/dose x Child Weight in kg

Based on BSA

Dosage for children based on body weight alone may often result in an insufficient amount, whereas dosing based on body surface area yields a more accurate result and a higher quality research study. At one year of life, BSA becomes a more reliable indicator of organ development and physiological function than does body weight.

Dosing chemotherapeutic medicines often involves a second verification step (BSA calculation) before administration. When the child’s height and weight are determined, the West Nomogram may aid with this.


  • Child dose by BSA (mg/day) = Adult Dose in mg/mx BSA in m2

Based on Young’s rule

Except during the earliest years of life and puberty, the body weight rule may be approximated by using Young’s method for pediatric dose. This rule should not be applied to infants, and the fact that there is always some degree of growth fluctuation at any age should be taken into account.


  • Child dose by Young’s rule (mg/day) = Adult Dose (mg/day) x [Age / (Age+12)]

Based on Clark’s rule

Clark’s rule is a pediatric dosing guideline based on weight proportions relative to the average adult. Hence, the child’s weight is measured in pounds rather than kilograms for this approach.


  • Child dose by Clark’s rule (mg/day) = Adult Dose (mg/day) x (Child Weight in Lbs /150)