Calculate weight-based drug dosage and infusion volume. For educational reference only.
A drug dosage calculator finds the correct dose of a medication for a given patient based on weight, age, or body surface area (BSA), and computes IV infusion rates for the prescribed dose. Paediatric and oncology dosing in particular requires weight-based calculation; adult fixed-dose pills are simpler but still require infusion rate math for IV therapy.
Drug dosage errors are one of the top three preventable patient safety incidents in hospitals worldwide. Always double-check the calculation, the dose, the route, the time, and the patient — the "5 rights" of medication administration.
\text{Rate (mL/h)} = \frac{\text{Dose (mg/h)}}{\text{Concentration (mg/mL)}}
Inputs: 70 kg patient · noradrenaline infusion at 0.1 mcg/kg/min · concentration 8 mg in 100 mL saline
For most adult oral medications, rounding to the nearest tablet strength is standard practice. For paediatric, neonatal, and high-risk drugs (insulin, heparin, opioids, vasopressors), use the calculated dose with at most 1 decimal place of rounding. NEVER round to a whole number for paediatric weight-based doses — a 4 kg neonate getting a "5 kg dose" is a 25% overdose.
Body Surface Area dosing (Dubois formula: BSA = 0.007184 × Wt^0.425 × Ht^0.725) is the standard for oncology chemotherapy, where toxicity correlates more closely with BSA than with weight alone. It is also used for some cardiac index measurements and for certain critical care drug calculations. For routine clinical practice, weight-based dosing is sufficient for nearly all other indications.
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