Pediatric Dose Calculator

Calculate paediatric doses by weight and body surface area.

About Pediatric Dose Calculator

Weight-based dosing suits most drugs while surface area dosing is used where clearance tracks metabolic rate, notably in oncology. Clark's rule is a rough scaling and is generally superseded by explicit paediatric dosing. Children are not small adults: organ maturity and body composition change clearance in ways simple scaling cannot capture, which is why paediatric-specific dosing exists.

Formula

Pediatric Dose

Mosteller BSA = √(height × weight ÷ 3,600); Clark's rule = weight ÷ 70 × adult dose

Mosteller formula: The most widely used body surface area estimate
Clark's rule: Scales the adult dose by weight relative to a 70 kg adult

Worked example

With the default values below, Pediatric Dose Calculator returns Weight-Based Dose of 270.00. Change any input above and every figure here is recalculated in your browser.

Inputs used

Child weightminimum 0.1 kg: 18 kg
Child heightminimum 10 cm: 105 cm
Dose per kilogramminimum 0 mg/kg: 15 mg/kg
Dose per square metreminimum 0 mg/m2: 400 mg/m2
Adult dose for comparisonminimum 0 mg: 500 mg

Results

Weight-Based Dose: 270.00 mg
Body Surface Area: 0.7246 m2
Surface Area Based Dose: 289.83 mg
Clark's Rule Dose: 128.57 mg
Share of the Adult Dose: 54.00%

Step by step

1Values used
2Pediatric Dose
3Weight-Based Dose= 270.00 mg
4Body Surface Area= 0.7246 m2
5Surface Area Based Dose= 289.83 mg
6Clark's Rule Dose= 128.57 mg
7Share of the Adult Dose= 54.00

Assumptions and limits

The result is derived only from the 5 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
This performs arithmetic on figures you supply and does not recommend any drug, dose or route. Medication errors can cause serious harm or death. Always verify every calculation independently, confirm against the prescription and product literature, and follow your institution's double-check procedures. Never self-medicate or alter a prescribed dose. Paediatric dosing carries particular risk because of narrow margins and rapid weight changes. Always use paediatric-specific prescribing references and confirm with a paediatric pharmacist or prescriber.
This is an estimate for general information and not professional medical advice. See the full disclaimer for the limits that apply to this kind of calculator.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

This performs arithmetic on figures you supply and does not recommend any drug, dose or route. Medication errors can cause serious harm or death. Always verify every calculation independently, confirm against the prescription and product literature, and follow your institution's double-check procedures. Never self-medicate or alter a prescribed dose. Paediatric dosing carries particular risk because of narrow margins and rapid weight changes. Always use paediatric-specific prescribing references and confirm with a paediatric pharmacist or prescriber.

Frequently Asked Questions

How is Pediatric Dose calculated?

Mosteller BSA = √(height × weight ÷ 3,600); Clark's rule = weight ÷ 70 × adult dose Weight-based dosing suits most drugs while surface area dosing is used where clearance tracks metabolic rate, notably in oncology. Clark's rule is a rough scaling and is generally superseded by explicit paediatric dosing.

Why does Pediatric Dose matter?

Children are not small adults: organ maturity and body composition change clearance in ways simple scaling cannot capture, which is why paediatric-specific dosing exists.

What values do I need to enter?

This calculator takes 5 inputs: Child weight, Child height, Dose per kilogram, Dose per square metre, Adult dose for comparison. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.