Drug Dosage Calculator

Weight-based dosing translates a patient's body weight and a prescribed dose per kilogram into a single, defensible number. Treat the figures here as an educational illustration of how the arithmetic works, not as clinical guidance for administering medication.

The math itself is simple multiplication: take the patient's weight in kilograms and multiply it by the ordered dose per kilogram, such as mg/kg. A drug prescribed at 5 mg/kg for someone weighing 70 kg therefore yields 350 mg per dose. Orders are written either per dose or per day, so the calculator asks which one yours is. Per dose, it multiplies the per-dose result by the doses per day to get the daily total; per day, it treats weight × mg/kg as the daily total and divides it across the doses. Entering a per-day order as per-dose would multiply every dose by the number of doses a day. Pharmacology relies on this same weight-based relationship across countless agents, which is exactly why a clean, consistent calculation matters.

Unit confusion is a well-documented source of weight-based dosing errors: recording a 220 lb patient as 220 kg instead of 100 kg produces a more-than-twofold overdose, which is why the National Coordinating Council for Medication Error Reporting and Prevention recommends documenting weights in metric units only. Mixing up kilograms and pounds, or milligrams and micrograms, can quietly distort the result, and a single misplaced decimal can produce a tenfold overdose or underdose. Because individual patient factors shape what the right dose actually is, the values shown here are for learning only and any real administration belongs in the hands of a healthcare professional.