Clark's Rule Calculator (Educational & Exam Reference)
Estimates paediatric dose from adult dose using weight in pounds (lb) or kg for academic/GPAT examination preparation.
⚠️ Educational Calculation & Clinical Safety Safeguard: EDUCATIONAL / HISTORICAL FORMULA ONLY: In clinical practice, always use validated drug-specific mg/kg or BSA paediatric dosing. Educational calculations do not replace clinician assessment, patient-specific laboratory monitoring, or institutional prescribing protocols.
Interactive Calculator
Allowed physiological/compounding range: 2 to 70 kg
Allowed physiological/compounding range: 1 to 5000 mg
Calculated Output (mg)
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Step-by-Step Mathematical Derivation & Explanation:
Validated Formula & Conversion Rules
Clark's Rule: Child Dose = [Weight in lb / 150] × Adult Dose (where Weight in lb = kg × 2.2) ≈ [Weight in kg / 68.18] × Adult DoseWorked Clinical Example
20 kg child (44 lb), Adult Dose 500 mg: Child Dose = (44 / 150) × 500 = 146.67 mg.
Rounding Rules, Assumptions & Source References
- Rounding Rule: For examination MCQs, note whether 1 kg = 2.2 lb (150 lb ≈ 68 kg) or 70 kg denominator is specified.
- Clinical Assumptions & Limitations: Validated only within the stated physiological input boundaries. For paediatric, renal (Cockcroft-Gault), and critical-care infusion calculations, always cross-check against official product labelling and institutional guidelines.
- Source References: Indian Pharmacopoeia (IP 2022), National Formulary of India (NFI), British National Formulary (BNF), and NCBI Bookshelf Clinical Pharmacology Compendia.