The paediatric drug dosage calculator computes the dose per administration and total daily dose for children based on the prescribed mg/kg dose and the child's body weight. Weight-based dosing is used for virtually all medications in paediatric practice because children's pharmacokinetics differ substantially from adults — particularly in neonates and infants. Always verify paediatric doses against a current reference such as the BNF for Children (BNFc) or Harriet Lane Handbook before administration.
| Drug | Typical Dose | Route |
|---|---|---|
| Paracetamol / Acetaminophen | 15 mg/kg Q4-6H (max 75 mg/kg/day) | PO/PR |
| Ibuprofen | 5–10 mg/kg Q6-8H (max 40 mg/kg/day) | PO |
| Amoxicillin | 25–45 mg/kg/day in 2–3 divided doses | PO |
| Ceftriaxone | 50–100 mg/kg/day (max 4g/day) | IV/IM |
| Salbutamol (Albuterol) | 0.1–0.15 mg/kg Q4-6H (max 2.5mg) | Nebulised |
Total dose per administration, calculated as dose per kg × weight. These illustrate the arithmetic only — the actual dose, frequency, and maximum for any child must come from a current paediatric formulary and the prescription in front of you.
| Child's weight | 10 mg/kg | 15 mg/kg | 20 mg/kg | 30 mg/kg |
|---|---|---|---|---|
| 5 kg | 50 mg | 75 mg | 100 mg | 150 mg |
| 10 kg | 100 mg | 150 mg | 200 mg | 300 mg |
| 15 kg | 150 mg | 225 mg | 300 mg | 450 mg |
| 20 kg | 200 mg | 300 mg | 400 mg | 600 mg |
| 25 kg | 250 mg | 375 mg | 500 mg | 750 mg |
| 30 kg | 300 mg | 450 mg | 600 mg | 900 mg |
| 40 kg | 400 mg | 600 mg | 800 mg | 1,200 mg |
Children are the group where a decimal point in the wrong place does the most damage. An adult given ten times a paracetamol dose is in trouble; a 5 kg infant given ten times theirs is in a different category of trouble entirely, because there's no margin to absorb the error.
A few habits that catch most mistakes before they reach the patient:
Multiply the child's weight in kg by the prescribed dose in mg/kg to get the single dose. For example, paracetamol 15 mg/kg for a 20 kg child = 15 × 20 = 300 mg per dose. Multiply by daily frequency to get the total daily dose.
The standard dose of paracetamol for children is 15 mg/kg every 4–6 hours, with a maximum daily dose of 75 mg/kg/day (up to 4g/day in children over 50 kg). Always check the current BNFc or prescribing information for age and weight-specific limits.
Multiply the prescribed dose per kg by the child's current weight in kg. For example, 15 mg/kg for a 20 kg child is 15 × 20 = 300 mg per dose. Always check against the drug's stated maximum — the maximum wins even if the per-kg figure is higher.