Is Clark's rule more accurate than Young's rule?

Clark's rule, which uses body weight, is generally considered more precise than Young's rule, which uses age alone, because weight better reflects a child's drug distribution and metabolism. Neither is recommended over an established pediatric dose when one exists.

Pediatric Dose Calculator 2026:Better Integration, Dose verification and compounding Alert

By Abeera Bhatti, Pharm-D & Saba Saeed, Pharm-D, M.Phil
Pharmaceutical Science Specialists | Clinical Pharmacy Experts

Pediatric Dose Calculator — Weight, BSA, Young’s & Clark’s Rule | Free Clinical Tool

Dose by weight (mg/kg)

Adult / reference dose per kg

Enter a dose greater than 0.

Child’s weight

Valid range: 0.3–150 kg (≈0.7–330 lb).

Enter a weight between 0.3 kg and 150 kg.

Administration frequency

Doses per day

Optional checks

Available concentration (for a liquid volume)

e.g. 125 mg / 5 mL. Leave blank to skip volume conversion.

Maximum recommended dose (mg/day), if known

If provided, the result is flagged when the calculated dose exceeds this ceiling.

Result

Fill in the form and select Calculate to see the estimated dose.

For education and clinical decision support only — not a substitute for professional judgment. Always verify the result against an established pediatric dose, the product labeling, and the maximum single/daily dose before administering. Estimation formulas can misjudge doses in neonates, premature infants, and children at the extremes of the weight range; a pharmacist or prescriber should confirm any dose before it is given.

How pediatric dosing methods compare

There is no single formula that fits every child and every drug. When an established pediatric dose exists in the product labeling or a pediatric reference, use that instead of estimating from an adult dose. When no pediatric dose is available, these four estimation methods are the ones most often taught and used:

Weight-based (mg/kg)

The current clinical standard whenever pediatric trial data exists. Scales the dose directly to the child’s weight.

Dose = mg/kg × weight (kg)

Body surface area (BSA)

Preferred for chemotherapy and other narrow-therapeutic-index drugs, since organ function tracks BSA more closely than weight alone above age 1.

Dose = Adult dose × BSA ÷ 1.73

Young’s rule

An age-based estimate. Now considered a historical teaching method rather than a clinical standard, and unsuitable for infants.

Dose = Adult dose × age ÷ (age + 12)

Clark’s rule

A weight-fraction estimate, generally more precise than Young’s rule but still considered historical compared with mg/kg or BSA dosing.

Dose = Adult dose × weight (lb) ÷ 150

Frequently asked questions

Which method should I trust the most?

Weight-based (mg/kg) dosing built on actual pediatric clinical trial data is the current standard of care. BSA dosing is preferred for oncology and other narrow-therapeutic-index drugs. Young’s rule and Clark’s rule are useful for understanding dosing history and for exam preparation, but modern guidelines favor mg/kg or BSA methods whenever pediatric-specific data is available.

Why does this calculator ask for height as well as weight?

The BSA method uses the Mosteller formula, BSA (m²) = √(height in cm × weight in kg ÷ 3600), which needs both measurements to estimate body surface area.

What if my calculated dose exceeds the maximum dose I entered?

The tool flags this clearly in the results and in the downloaded report. A result above a known maximum should be rechecked against the product labeling and discussed with a pharmacist or prescriber before administration — never given as calculated without that check.

Can I use this for neonates or premature infants?

No. Neonates and premature infants have immature hepatic and renal function and require dosing from neonatal-specific references, not adult-dose extrapolation formulas.

References

Mosteller RD. Simplified calculation of body-surface area. N Engl J Med. 1987;317(17):1098.
Traub SL, Johnson CE. Comparison of methods of estimating creatinine clearance in children. Am J Hosp Pharm. 1980;37(2):195–201 (background on weight/BSA scaling in pediatric pharmacokinetics).
World Health Organization. WHO Model Formulary for Children. Geneva: WHO Press.
American Academy of Pediatrics, Committee on Drugs. Policy statements on safe and effective pediatric medication use. Pediatrics.
Taketomo CK, Hodding JH, Kraus DM. Pediatric & Neonatal Dosage Handbook, Lexicomp.
Kliegman RM, et al. Nelson Textbook of Pediatrics, chapter on principles of drug therapy in infants and children.
Contemporary pharmacology sources note that Young’s and Clark’s rules are historical estimation methods, with weight-based (mg/kg) and BSA dosing considered the modern standard whenever pediatric-specific data exists.

Our Team of Pharmacists working in various Healthcare organizations came across a number of pediatric emergencies, the major challenge at that time is not to provide the basic support and medication but to provide the accurate dosage to minimise the potential side effects and over-dose poisoning. With the Collaborative Efforts of our team we have developed this tool for calculating pediatric dosage, it is accurate (cross-checked multiple times with manual calculations), Used widely in various healthcare set ups, endorsed by number of organizations and above all, it is fast which can help to uplift culture of safety and security.

Pediatric Dose Calculator 2026:Better Integration, Dose verification and compounding Alert

Result

How pediatric dosing methods compare

Weight-based (mg/kg)

Body surface area (BSA)

Young’s rule

Clark’s rule

Frequently asked questions

References

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