Medication Dosage Calculator

About weight-based dosage calculations

Weight-based medication dosing expresses an ordered amount relative to body mass, often in milligrams per kilogram. This calculator performs the arithmetic after a clinician, pharmacist, or authoritative protocol has already supplied the correct milligrams-per-kilogram dose and dosing frequency. It multiplies weight in kilograms by the ordered dose to find milligrams for one administration, then multiplies by the number of daily administrations to find the total daily amount. If weight is entered in pounds, the calculator converts it to kilograms using 2.2046226218 pounds per kilogram. The entered dose must specifically be in milligrams per kilogram per dose. That distinction matters because some references instead state milligrams per kilogram per day and then divide the daily amount into several administrations. Treating a daily recommendation as a per-dose recommendation could multiply the intended amount and create a dangerous error. The optional maximum daily dose provides a simple comparison. When the calculated total exceeds that number, the tool displays a warning. It does not automatically cap or change the result because medication protocols differ and clinical decisions must remain visible. A maximum may depend on indication, age, kidney or liver function, route, formulation, treatment duration, interacting medicines, and local guidance. Never invent a maximum or assume that a common adult maximum applies to a child. This result is not a prescription and does not identify an appropriate drug, dose, schedule, or duration. It does not account for allergies, contraindications, renal adjustment, hepatic adjustment, pregnancy, prematurity, obesity dosing weight, therapeutic drug monitoring, or concentration. It also reports milligrams, not tablets or liquid volume. Converting milligrams to a volume requires the exact concentration printed on the dispensed product, and products with similar names may have different strengths. Medication errors can cause serious harm. Before administration, verify the patient, medicine, indication, current weight, units, route, dose source, frequency, maximum, formulation concentration, and decimal placement. Use a leading zero for values below one and avoid trailing zeros that can be misread. Have high-risk or pediatric calculations independently checked according to professional policy. If an order is unclear, a result seems unusual, or the calculated amount conflicts with labeling, stop and contact a pharmacist or prescriber rather than relying on this calculator.

Dosage calculation examples

How to calculate a medication dosage

1. Confirm that the authorized dose is stated in milligrams per kilogram per dose.
2. Enter the current patient weight and choose kilograms or pounds.
3. Enter the prescribed dose, daily frequency, and any applicable maximum daily amount.
4. Select Calculate Dosage, then independently verify the result and all units before use.

Medication dosage FAQ