Pediatric Dose Calculator
Work out a weight-based medication dose from a mg/kg order. Enter the child’s weight and the dose per kilogram to get the amount per dose and per day, apply an optional maximum, and convert to a volume in millilitres if you enter the liquid concentration. This is a general dosing-arithmetic tool — it does not know the correct mg/kg for any specific drug, which comes from a paediatric formulary.
About weight-based dosing
Weight-based (mg/kg) dosing is standard in paediatrics because drug requirements scale with body size, with an absolute maximum so a child never exceeds an adult dose. This calculator turns an order into the per-dose, daily and volume amounts to reduce arithmetic errors; the correct mg/kg and maximum come from a current formulary. This is an educational reference, not medical advice.
Frequently asked questions
How is a weight-based dose calculated?
Dose per administration = weight (kg) × the dose per kilogram (mg/kg). The daily dose is that amount multiplied by the number of doses per day. For example, 15 mg/kg in a 20 kg child is 300 mg per dose; given three times a day that is 900 mg/day. This calculator does the arithmetic and, if you enter a maximum, caps the per-dose amount at it.
Where does the mg/kg figure come from?
From a paediatric drug reference or formulary for the specific medicine and indication — this calculator does not supply it. Many drugs have both a per-dose mg/kg and a maximum per dose (often the usual adult dose), and some are dosed by mg/kg/day divided into several doses rather than per dose. Enter the values from your source; if you are dosing per day, put the mg/kg/day figure in and set doses per day to 1 to read the daily total.
How do I convert the dose to millilitres?
Enter the liquid concentration as milligrams per millilitre — for a suspension labelled “250 mg/5 mL” that is 50 mg/mL. The volume per dose is then the dose in mg divided by the concentration. So a 300 mg dose of a 50 mg/mL suspension is 6 mL. Always double-check the concentration on the actual bottle, as the same drug comes in several strengths.
Should I use actual or ideal body weight?
Most paediatric dosing uses actual body weight, but some drugs in older or overweight children use ideal or adjusted body weight, and many have an absolute maximum so the child never receives more than an adult dose. Follow the guidance in the formulary for that drug. This tool applies whatever weight and maximum you enter.
Is this a substitute for checking the dose?
No. It is dosing arithmetic to reduce calculation errors, not a source of correct doses, and it does not check for age limits, contraindications or drug interactions. Paediatric doses should be verified against a current formulary and, in practice, independently double-checked. This is an educational reference, not medical advice.
This is a reference tool, not a diagnosis or medical advice. Results depend on the laboratory, assay and clinical context, and reference intervals vary between labs and by age and sex — always read your result against the range printed on your own report and discuss it with a qualified healthcare professional.
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