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Medication dosage by weight calculator (mg/kg)

Calculate the total dose from the recommended dose per kg and the patient's weight.

kg
mg/kg
Dose per intake
300 mg
Total per day300 mg

⚠️ Guidance only. Does NOT replace a prescription or the label. Confirm with a professional.

How the calculation works

Many medications (especially in pediatrics) are dosed per kilogram of body weight. The math is direct:

dose = weight (kg) × dose per kg

For the daily total, multiply by the number of intakes per day.

Step-by-step example

A 20 kg child, drug at 10 mg/kg, 3 times a day:

  • Per dose: 20 × 10 = 200 mg
  • Per day: 200 × 3 = 600 mg

Important: this is a checking tool. The correct dose, interval and maximum depend on the drug, age and condition. Always confirm with a doctor or pharmacist and follow the prescription.

Examples

  • Adult 70 kg, 15 mg/kg: 1,050 mg per dose.
  • Infant 8 kg, 5 mg/kg: 40 mg per dose.

Frequently asked questions

Any medication?

Only when the label gives a per-kg dose. Always confirm with a professional.

How to convert the dose to mL of syrup?

Divide the mg dose by the syrup concentration (mg/mL). E.g. 200 mg in a 50 mg/mL syrup = 4 mL. Always check the label.

Real or ideal weight?

It depends on the drug — some use adjusted weight or lean mass. That is set by the prescription, not this calculator.

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Updated on June 18, 2026 · by Rafael Rossi · Methodology & sources