Pediatric Dosage Calculator
Calculate pediatric drug doses from standard adult dosages based on the child's body weight using Clark's Rule.
About Clark's Pediatric Dosage Rule
Clark's Rule is an established clinical medical formula used to calculate a safe pediatric medication dose when a weight-specific child dosage schedule is not explicitly outlined by the manufacturer.
Formula
Pediatric Dose = [ Child Weight in Lbs / 150 ] × Adult Dose
Expressed in metric kilograms: [ Child Weight (kg) × 2.20462 / 150 ] × Adult Dose
Worked Example
For a 20 kg child (44.1 lbs) where the standard adult dosage is 500 mg:
Dose = (44.09 / 150) × 500 mg = 0.294 × 500 = 147 mg
Frequently Asked Questions
Is Clark's Rule suitable for neonates and infants under 1 year?
No. Neonates possess immature hepatic cytochrome P450 enzymes and underdeveloped renal filtration, requiring strict mg/kg specialist dosing protocols.
How does Clark's Rule compare to Young's Rule?
Young's Rule calculates doses based on age, whereas Clark's Rule uses weight. Weight-based dosing is generally more accurate for pediatric populations.
Should pediatric suspensions be measured with household spoons?
Never. Household kitchen spoons vary widely in volume; always administer pediatric liquid suspensions with calibrated oral syringes.
Can this calculator replace pediatrician instructions?
No. This tool provides historical mathematical approximations and should not override a licensed physician's prescription.
Calculate in three steps
- 1Enter your valuesUse the fields above and check the units shown beside each input.
- 2Run the calculationSelect Calculate to refresh the result with your latest values.
- 3Review or shareCompare the result, reset the form, print it, or share this page.