Enter the adult dose and the child’s age at next birthday into the calculator to determine the child’s dose. This calculator can also evaluate any of the variables given the others are known.
Safety note: Educational use only—this is not medical advice. Do not use this tool to dose medication for a child. Pediatric dosing should follow the specific medication label and a clinician/pharmacist’s instructions (often weight-based mg/kg with maximum doses, route, and schedule). This calculator does not account for per-dose vs per-day directions or liquid concentration (mg↔mL). If you suspect an overdose, contact local emergency services or poison control immediately.
Cowling’s Rule Formula
The following formula is used to estimate the appropriate dosage of medication for children according to Cowling’s Rule.
CD = (AD * A) / 24
Variables:
- CD is the child’s dose (mg)
- AD is the adult dose (mg)
- A is the child’s age at next birthday (years)
To calculate the child’s dose, multiply the adult dose by the child’s age at next birthday (in years). Then, divide the result by 24. This will give an age-based estimate of the child’s dose according to Cowling’s Rule. However, this rule should be used with caution as it is a historical rule-of-thumb and may not be accurate for all medications and age groups (especially infants and very young children).
What is Cowling’s Rule?
Cowling’s Rule is an age-based pediatric dosing rule-of-thumb that estimates a child’s dose from an adult dose using the child’s age at next birthday. The rule is: child’s dose = adult dose × (age at next birthday / 24). Because modern pediatric dosing is typically based on weight (and sometimes body surface area) and specific drug guidance, Cowling’s Rule should be used with caution and is not appropriate for all medications or patients.
How to Calculate Cowling’s Rule?
The following steps outline how to calculate the Cowling’s Rule.
- First, determine the adult dose (AD) in milligrams (mg).
- Next, determine the child’s age at next birthday (A) in years.
- Next, use the formula CD = (AD * A) / 24 to calculate the child’s dose (CD) in milligrams (mg).
- Finally, calculate the result.
- 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.
adult dose (AD) = 200 mg
child’s age at next birthday (A) = 8 years, so child’s dose (CD) = (200 × 8) / 24 = 66.67 mg
