Pediatric Medication Dosage Calculator
Calculates the correct medication dose for a child based on their weight and the prescribed dose per kilogram. Used by parents, nurses, and caregivers to prepare accurate doses of common pediatric medicines.
About this calculator
Most pediatric medications are dosed on a per-kilogram basis to account for differences in body size and drug metabolism between children. The core formula is: Total Dose (mg) = Child's Weight (kg) × Dose per kg (mg/kg). The prescriber or drug reference provides the dose-per-kg value, which varies by medication, condition, and age group. Maximum dose caps (adult doses) often apply and must always be checked — this calculator computes weight-based dose only and does not enforce caps automatically. For liquid medications, an additional step is needed: Volume (mL) = Total Dose (mg) / Concentration (mg/mL). Accurate weight measurement is critical because even small errors in weight can result in significant dosing errors in young children.
How to use
Example: A child weighs 20 kg and has been prescribed ibuprofen at 10 mg/kg per dose. Step 1 — Enter weight: 20 kg. Step 2 — Enter dose per kg: 10 mg/kg. Step 3 — Apply the formula: Total Dose = 20 × 10 = 200 mg per dose. Step 4 — If using a liquid suspension of 100 mg/5 mL (20 mg/mL), calculate volume: 200 / 20 = 10 mL per dose. Always verify the calculated dose does not exceed the maximum recommended dose stated in the prescribing information or drug leaflet.
Frequently asked questions
Why are pediatric medication doses calculated per kilogram of body weight?
Children are not simply small adults — their body composition, organ maturity, and metabolic rates differ significantly from adults and change rapidly with age. Dosing by weight ensures that the amount of drug relative to the child's body size remains within a therapeutic range that is effective without being toxic. A flat dose appropriate for a 30 kg child could dangerously overdose a 10 kg toddler or undertreat a larger adolescent. Weight-based dosing is the international standard for pediatric pharmacotherapy.
How do I convert a pediatric weight-based dose from mg to mL for a liquid medicine?
Once you have calculated the total dose in milligrams using Total Dose = weight × dose per kg, divide it by the concentration of the liquid formulation: Volume (mL) = Total Dose (mg) ÷ Concentration (mg/mL). The concentration is printed on the medicine label, often expressed as mg per 5 mL. For example, if the concentration is 250 mg/5 mL, the equivalent is 50 mg/mL, and a 200 mg dose requires 200 ÷ 50 = 4 mL. Always use a calibrated oral syringe, not a household spoon, for accurate measurement.
What is the maximum dose I should give a child even if the weight-based calculation is higher?
Most pediatric drug guidelines specify a maximum single dose or daily dose that mirrors the standard adult dose, regardless of weight. This cap exists because drug clearance, receptor sensitivity, and toxicity thresholds eventually plateau and do not continue to scale linearly with weight. For example, ibuprofen is typically capped at 400 mg per dose for children even if the weight-based calculation exceeds that. Always cross-check your calculated dose against the maximum dose listed in the product information or consult a pharmacist or prescriber.