Paediatric medicine doses are always weight-based — unlike adults, where one fixed dose fits most. A dose that is too high causes serious adverse effects; a dose too low leaves the child untreated.
This article walks through the calculation for the three most common children's drugs: paracetamol, ibuprofen and amoxicillin. You will learn the formulas, daily maxima, typical syrup concentrations and safety warnings.
Important: this is not medical advice. Paediatric dosing must be confirmed by a licensed clinician or pharmacist.
The core formula
Every weight-based paediatric dose follows one simple rule:
Dose (mg) = body weight (kg) × mg per kg
For converting to syrup volume:
Volume (mL) = dose (mg) ÷ concentration (mg/mL)
Paracetamol
- Single dose: 10–15 mg/kg
- Daily maximum: 60 mg/kg/day (max 4 g for larger children)
- Interval: every 4–6 hours, max 4 doses/day
- Syrup concentration: typically 24 mg/mL
- Example: 20 kg × 15 mg/kg = 300 mg = 12.5 mL of syrup
Paracetamol is approved from birth. Note: an overdose can cause severe liver damage even when initial symptoms are absent.
Ibuprofen
- Single dose: 7–10 mg/kg
- Daily maximum: 30 mg/kg/day (max 2.4 g)
- Interval: every 6–8 hours
- Syrup concentration: 20 mg/mL or 40 mg/mL
- Example: 15 kg × 10 mg/kg = 150 mg = 7.5 mL at 20 mg/mL
Ibuprofen is approved from 3 months of age and a minimum weight of 5 kg. For younger infants prefer paracetamol.
Amoxicillin
- Standard dose: 20–45 mg/kg/day, divided into 2–3 doses
- High dose (e.g. otitis media): 80–90 mg/kg/day
- Interval: every 8–12 hours
- Syrup concentration: 50 mg/mL (typical suspension)
Standard vs high-dose depends on age, pathogen and indication. Always prescribed by a clinician.
Safety warnings
- Weight under 3 kg: neonates require clinician-supervised dosing — never self-dose.
- Weight over 80 kg: likely an adult — use adult dosing rather than the paediatric mg/kg formula.
- Above the recommended single dose: never exceed the dose listed in the package insert — there is no upward "safety margin".
- Suspected overdose: contact poison control or emergency services immediately.
Related calculators
- Growth percentiles — compare a child's weight and height with WHO reference curves. Visit the child growth percentile calculator.
- Body surface area — some drugs are dosed per BSA (e.g. oncology). Visit the BSA calculator.
- BMI — body mass index for older children and adolescents. Visit the BMI calculator.
Calculate the dose now
Pick the drug, enter the weight — instant single dose and daily maximum in mg and mL.
Open child dosage calculator →Frequently asked questions
How is paediatric dose calculated?
The standard formula is dose (mg) = body weight (kg) × mg per kg. Paracetamol uses 10–15 mg/kg per single dose, ibuprofen 7–10 mg/kg. These come from paediatric prescribing references.
How many mL of syrup should I give?
Volume (mL) = dose (mg) ÷ concentration (mg/mL). 300 mg paracetamol at 24 mg/mL = 12.5 mL of syrup.
What is the maximum daily dose?
Paracetamol max 60 mg/kg/day (max 4 g), ibuprofen max 30 mg/kg/day (max 2.4 g), amoxicillin 20–90 mg/kg/day depending on indication.
From what age is ibuprofen allowed?
Ibuprofen is approved from 3 months of age and a minimum weight of 5 kg. Younger infants should use paracetamol instead.