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About this tool
Turn a mg-per-kg instruction into a total daily dose, a per-dose amount and a syrup volume, with optional maximum-dose caps.
The Weight-Based Dose Converter turns a prescription written per kilogram — for example 30 mg/kg/day in three divided doses — into the actual milligrams for one body weight, then into a millilitre volume when the medicine is a liquid. It works from the plain arithmetic dose = strength per kg × weight in kg, converts pounds using the exact 0.45359237 kg factor, and divides by the number of doses per day. It is a calculation aid for carers and students, not a drug reference: it holds no dose limits of its own.
Open Weight-Based Dose Converter on AltFTool — it loads instantly in your browser.
Enter the values you already know.
Fine-tune the options to match your scenario.
Read the result and use it in your planning or reporting.
Handles per-day totals split into divided doses and straight per-dose instructions.
Enter the liquid strength as mg in mL and get the syringe volume, rounded to the 0.1 mL mark.
Optional single-dose and daily maximums are flagged clearly instead of being silently ignored.
Multiply the prescribed milligrams per kilogram by the body weight in kilograms. A 30 mg/kg/day instruction for a 20 kg child is 600 mg a day, which is 200 mg per dose when it is split into three. If the figure is written per dose rather than per day, multiply by the number of doses to get the daily total.
Divide pounds by 2.2046, or multiply by 0.45359237, which is the exact definition of the international pound. So 44 lb is 19.96 kg — using a rounded 20 kg would change a 15 mg/kg dose by about 0.6 mg.
Divide the dose in milligrams by the concentration in milligrams per millilitre. A 250 mg in 5 mL suspension is 50 mg/mL, so a 100 mg dose is 2 mL. Always read the strength from the bottle you actually have, because the same medicine is sold in several strengths.
Use a calculation like this only to check a dose that has already been prescribed or is printed on the label, never to decide one. Dosing depends on the drug, the indication, kidney and liver function and the maximum limits for that product. Confirm every paediatric dose with a pharmacist or prescriber.
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