Clinical & Hospital Pharmacy
Pediatric Dosing Calculator
Calculates a child's dose by body weight (mg/kg) and compares it with the classic Young's, Clark's and Fried's rules.
Dose · mg/kg dose
300.0mg
Appropriate pediatric dose range
Patient & dose
Try a drug preset
≈ 44.1 lbs
≈ 60 months
Per-kg single dose target, from the formulary.
Standard 70 kg adult dose — used for % of adult dose and the other rules.
Dose check
Your values in the formula, and how the dose compares.
Appropriate pediatric dose range
Multi-rule comparison
The same child and doses through all four methods.
| Rule | Dose | mg/kg |
|---|---|---|
| mg/kg StandardActive | 300.0 mg | 15.0 |
| Young's (Age) | 147.1 mg | 7.4 |
| Clark's (Weight) | 147.0 mg | 7.3 |
| Fried's (Infants) | 200.0 mg | 10.0 |
mg/kg: Dose = target (mg/kg) × weight (kg)
Safest and most widely accepted in current clinical practice.
Young's rule: Dose = [age (years) / (age + 12)] × adult dose
Based on age, for children aged 1–12. Tends to underestimate for older children.
Clark's rule: Dose = [weight (lbs) / 150] × adult dose
Assumes a standard adult weighs 150 lbs (68–70 kg). Weights entered in kg are converted (1 kg = 2.20462 lbs).
Fried's rule: Dose = [age (months) / 150] × adult dose
Developed for infants under 1–2 years.
For the three rules, the dose check compares the child's mg/kg with the adult dose spread over 70 kg: above 1.75× that figure is flagged high, below 0.35× low.
Keep learning
References
- Stockton SJ. Stoklosa and Ansel's Pharmaceutical Calculations. 16th ed. Philadelphia: Wolters Kluwer; 2021.
Common questions
mg/kg, with the target taken from a paediatric formulary for that drug and indication. Young's, Clark's and Fried's rules predate modern paediatric pharmacokinetics; they are useful for exams and as a rough cross-check, not for choosing a real dose.
It depends on the reference. Paracetamol is quoted per dose (15 mg/kg every 4–6 h); amoxicillin and prednisolone are often quoted per day, then divided. This calculator multiplies whatever mg/kg you enter by the weight — divide a daily total into doses yourself.
Each scales the adult dose by a different proxy — age in years, age in months, or weight — and none accounts for how drug clearance actually matures. The comparison table makes that spread visible.
Yes. Switch the unit next to weight to lbs. The calculator converts to kg for mg/kg and uses pounds directly for Clark's rule.
It appears only for the three historical rules. It compares the child's calculated mg/kg with the adult dose divided by 70 kg; a large difference suggests the rule is a poor fit for this child and a formulary dose should be checked.
Prepared by the PharmaWallah student team. Verify results with your textbook or instructor. Report an error · Editorial policy