Enter the age of the child and the standard adult dosage into the calculator to determine the child’s dosage.

Young’s Rule Formula

The following formula is used to calculate the dosage of medicine for a child using Young’s Rule.

Dc = (A * D) / (A + 12)


  • Dc is the child’s dosage (mg) A is the age of the child (years) D is the standard adult dosage (mg)

To calculate the child’s dosage, multiply the age of the child by the standard adult dosage. Then divide the result by the sum of the child’s age and 12.

What is a Young’s Rule?

Young’s Rule is a formula used in medicine to calculate the correct dosage of medicine for a child. The rule is based on the child’s age and is used to proportionally adjust the adult dosage to a suitable amount for a child. The formula is: Child’s dose = (Age of child / (Age of child + 12)) x Adult dose. This rule is commonly used in pediatrics, although it is considered less accurate than dosage calculations based on body weight.

How to Calculate Young’s Rule?

The following steps outline how to calculate the Young’s Rule for a child’s dosage.

  1. First, determine the age of the child (A) in years.
  2. Next, determine the standard adult dosage (D) in mg.
  3. Next, use the formula Dc = (A * D) / (A + 12) to calculate the child’s dosage (Dc).
  4. Finally, calculate the child’s dosage (Dc).
  5. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

Age of the child (A) = 8 years

Standard adult dosage (D) = 200 mg