💊 Weight-Based Drug Dosage

Written and maintained by the PhDino author · Last reviewed 21 September 2026 · Checked against 1 independent reference calculation · how PhDino checks its numbers

Scaling a medication dose to a patient's body weight using a per-kilogram dosing rate.

Many medications, especially in pediatrics and critical care, are dosed by body weight rather than as a single fixed adult dose, since how a drug distributes through and gets cleared from the body scales substantially with body size. A dosing guideline expressed as milligrams per kilogram lets the same guideline apply sensibly across a wide range of patient sizes.

The per-kilogram dosing rate itself is a value that comes from clinical pharmacology research and published dosing guidelines specific to each drug and indication — it isn't something derived or estimated here, only applied once known.

Key formula

Total dose = patient weight (kg) × dose per kilogram (mg/kg)

Notes & limitations

• This performs the arithmetic only — it does not supply, verify, or validate the per-kilogram dosing rate itself, which must come from a verified drug reference or prescribing guideline for the specific medication and indication.
• Many drugs also have a maximum total dose that caps the weight-based calculation for larger patients (a dose that would otherwise keep scaling up indefinitely with weight) — checking that ceiling is a separate step this calculator doesn't perform.