What this calculator does
The Pediatric Weight-Based Dose Calculator converts a prescribed weight-based dose (in mg/kg) into the actual milligram dose for a child of a given body weight, then calculates the liquid volume (in mL) to measure out based on the medication's concentration. It also totals the dose and volume across all doses given in a day. This is an educational aid only — always confirm the final dose, maximum limits, and product concentration with a pharmacist or prescriber before administering any medication.
How to use it
Enter the child's weight in kilograms, the prescribed dose per kilogram (mg/kg), and the concentration of the liquid medication printed on the bottle (mg/mL). Optionally enter how many doses are given per day to see the daily totals. The calculator returns the dose per administration in milligrams and the matching volume in milliliters.
The formula explained
The per-dose amount is simply Dose = Weight × Dose per kg. To turn that milligram amount into a measurable liquid volume, divide by the concentration: Volume = Dose ÷ Concentration. Multiplying each by the number of doses per day gives the daily dose and daily volume, which is useful for checking against a maximum daily dose limit.
$$\text{Dose (mg)} = \text{Weight}_{kg} \times \text{Dose}_{mg/kg}, \quad \text{Volume (mL)} = \frac{\text{Dose}}{\text{Concentration}_{mg/mL}}$$
Worked example
A 20 kg child is prescribed 15 mg/kg of acetaminophen, available as a 100 mg/mL suspension, given 3 times daily. Dose = \(20 \times 15 = \) 300 mg. Volume = \(300 \div 100 = \) 3 mL per dose. Daily dose = \(300 \times 3 = 900\) mg, and daily volume = \(3 \times 3 = 9\) mL.
FAQ
Where do I find the concentration? It is printed on the medication label, e.g. "100 mg/5 mL" equals 20 mg/mL — divide the mg by the mL.
Does this check the maximum safe dose? No. It only performs the arithmetic. You must verify per-dose and per-day maximums against the drug reference for the child's age and weight.
What if my weight is in pounds? Convert to kilograms first by dividing pounds by 2.205, or enter the kilogram value directly.
