Calculator
Pediatric Dose Calculator
Children are not small adults. Two classic rules scale adult doses to children — Clark's Rule (by weight) and Young's Rule (by age). Clark's is preferred when weight is known.
Clark's Rule
1.67 mL
Young's Rule
2.00 mL
Round to a convenient increment. Start at the low end; increase if tolerated and needed. Under 2 years old, consult a pediatric herbalist.
Clark's rule
Child dose = Adult dose × (weight in lbs ÷ 150)
Treats a 150 lb adult as the reference. A 75 lb child gets half the adult dose; a 50 lb child gets one third. Closer to physiological reality than age alone.
Young's rule
Child dose = Adult dose × [age ÷ (age + 12)]
Age-based fallback when weight is not known. Reasonable between ages 2-12; less reliable for infants or tall/heavy children.
Practical cautions
- Under 2 years old: consult a practitioner. Formulas are rough; liver metabolism is still maturing.
- Some herbs (St John's Wort, ma huang, kava, comfrey, pennyroyal) are not appropriate for children at any scaled dose.
- Weight-based (Clark's) is more accurate when body size deviates from age averages.
- For drop-dose herbs (lobelia, belladonna homeopathy, etc.) the rules do not apply — use practitioner-specified pediatric dosing.