Paediatric Weight-Based Dosing

Pharmily+

This tool covers 20 common paediatric drugs and does the last mile most dosing tools skip — converting a weight-based dose into the actual liquid volume or tablet count for the specific formulation you have in stock. See How Calculator Tools Work for the shared layout.

Inputs

• Drug — search or select from the 20-drug list
• Weight (kg)
• Age (months)
• Formulation — the specific strength/form available (e.g. "125mg/5mL syrup"), if the drug has more than one

Two kinds of drugs in the list

Most of the 20 drugs are dosed by weight. A handful — zinc, folic acid, vitamin A, and albendazole — use fixed, age-banded doses instead (for example, zinc is 10mg once daily under 6 months of age and 20mg from 6 months on), so for those the tool skips the weight calculation and returns the correct fixed dose for the child's age directly.

For weight-based drugs

1. Daily dose = the drug's mg/kg/day × the child's weight.
2. Dose per administration = daily dose ÷ doses per day.
3. If that's more than the drug's maximum single dose, it's capped at the maximum with a warning telling you the uncapped figure was reduced.
4. The result is converted into what you actually measure out — a liquid volume in mL for syrups/drops, or a tablet count for tablets/capsules — based on the formulation you selected.

Other warnings you might see

• Below the drug's typical minimum age, even if above the neonatal block threshold — a prompt to verify the drug is appropriate for this age.
• Calculated dose under 1 mg — verify with a paediatric pharmacist before dispensing; doses this small are hard to measure accurately.
• Weight over 50 kg — consider adult dosing guidelines instead, since paediatric weight-based formulas aren't validated that high.

Reference

Nigeria STG 2022. BNF for Children.