Drug Dose Calculator (per kg)

Drug dose: dose = mg/kg · weight

Most of the time the clinical math starts from weight: dose (mg) = mg/kg · weight (kg). Oncology and pediatrics lean instead on body surface area (BSA): dose = mg/m² · BSA, where BSA comes from Mosteller's formula √(weight·height/3600). To dilute for IV use, volume (mL) = dose (mg) / concentration (mg/mL). And the drip rate for an infusion is drops/min = (total volume / time in min) · 20 drops/mL on a standard macro-drip set. A few familiar numbers: paracetamol runs 10–15 mg/kg every 4–6 h, capped at 4 g/day in adults; pediatric dipyrone 10–25 mg/kg; vancomycin 15–20 mg/kg with serum trough monitoring; gentamicin 3–7 mg/kg/day. IV antibiotics usually go into 0.9 % saline or 5 % dextrose, following whatever the package insert says.

Applications

It shows up in everyday prescribing, in electronic health records and CPOE systems, and in drug references like BulasMed, UpToDate and Micromedex. Pharmacists lean on it when verifying compounding, nurses use it for administration checks, and it carries the most weight in pediatric, neonatal and oncology dosing, where a slip has the worst consequences. Whatever the setting, double-check against a current reference and with the prescribing physician.

FAQ

Should I dose by actual or ideal body weight? It depends on the drug. Hydrophilic ones such as the aminoglycosides often go by ideal or adjusted body weight in obese patients, while lipophilic drugs use actual weight. Check the pharmacokinetic profile before deciding.

What's the maximum single dose? Every drug has its own ceiling. This calculator won't stop you at it, so verify against the package insert and the adult or pediatric tables.

How do I split the daily dose? Take the daily dose, divide by the number of fractions, and that's the dose per administration. For the spacing between doses, work from the drug's half-life and recommended posology.

Disclaimer: This is a mathematical aid, nothing more. It is no substitute for clinical judgment, the package insert or a prescriber. Confirm with a healthcare professional before acting on it.