Dose = weight in kg × mg/kg, then capped at the maximum single dose if you give one. The working shows the uncapped figure too, so a ceiling never silently swallows a decimal-point error.
It multiplies the numbers you give it. It carries no drug list, no age or renal adjustment, and no maximum of its own — the mg/kg and the ceiling come from your formulary, and the prescriber owns both.
It is a calculator, not a clinician. Nothing here is medical advice, and the person prescribing owns the decision.