Drug Dosage by Weight Calculator

This is a general-purpose weight-based dosing calculator, not a lookup table for any specific drug -- it performs the same core arithmetic that underlies mg/kg dosing for essentially every weight-based medication: Single Dose (mg) equals Patient Weight times the prescribed Dose per kg, and both scale it up proportionally, so heavier patients and higher per-kilogram doses both raise Single Dose in direct proportion. Daily Dose then multiplies that single dose by Frequency, the number of doses given per day. Drug Concentration only enters the picture for the two volume outputs -- Single Dose Volume and Daily Dose Volume, both in mL -- by dividing the milligram dose by the liquid formulation's concentration in mg/mL; a more concentrated formulation means a smaller volume delivers the same milligram dose. Critically, Drug Concentration and Frequency never change the milligram amounts themselves: Single Dose (mg) and Daily Dose (mg) come entirely from Patient Weight and Dose per kg, and adjusting concentration or frequency only reshapes how that fixed milligram amount is expressed or divided across the day, never how much drug is calculated in total per dose.

This calculator does not know the identity, indication, or safe dosing range of any particular medication -- the mg/kg dose and frequency entered must come from a verified prescribing reference, not from this tool, and results should always be double-checked against that reference before administration. Because it multiplies Dose per kg by whatever weight is entered with no built-in ceiling, an optional Max Daily Dose field is provided -- set it to a specific drug's published maximum (in mg/day) and the Exceeds Max Daily Dose flag will read true if the computed Daily Dose (mg) is over that ceiling; left at 0, the check is simply skipped, since this generic calculator has no per-drug maximum of its own. Total body weight dosing can also overstate the correct dose in obese patients: many real-world protocols instead dose by adjusted body weight (ABW) or ideal body weight (IBW) once a patient is significantly above ideal weight, precisely because scaling by total weight can multiply the dose far beyond what the drug's actual distribution volume calls for -- which weight convention applies is drug-specific and must come from the prescribing reference, not from this calculator. If Drug Concentration is missing or zero, the two volume outputs report as unavailable (rather than a misleading 0 mL) and the Drug Concentration Not Set flag reads true.