About this calculator
Weight-based medication dosing converts a prescribed mg/kg dose to a single dose and total daily amount. This calculator also converts to mL of liquid (given concentration) or tablets (given strength). It’s a unit-conversion sanity check — not medical advice and not a substitute for the prescribing label.
How weight-based dosing works
Single dose (mg) = patient weight (kg) × dose (mg/kg). Daily total = single dose × frequency. For liquid: mL = mg ÷ concentration. For tablets: tablets = mg ÷ tablet strength.
Common dosing examples
- Children’s acetaminophen — 10–15 mg/kg every 4–6 hours, max 5 doses/day. A 40 lb (18 kg) child: 180–270 mg/dose.
- Children’s ibuprofen — 5–10 mg/kg every 6–8 hours. Same 18 kg child: 90–180 mg/dose.
- Amoxicillin — 20–90 mg/kg/day depending on infection, divided 2–3×/day.
Why this calculator helps
Pharmacy labels give mg per dose; pediatric studies give mg/kg/dose. Translating between them while sleep-deprived with a sick child is error-prone. Cross-checking the math against this calculator (or any independent calculator) catches the occasional decimal-place error before it matters.
Critical safety notes
- Always use the dosing syringe that came with the medication — kitchen teaspoons vary by 50%+.
- Children’s ≠ infants’ ≠ adult formulations. Concentrations differ. Read the label every time.
- Acetaminophen max daily dose for adults: 3 g (per current liver-safety guidance, reduced from older 4 g recommendation).
- Combining multiple OTC products with overlapping ingredients (e.g., NyQuil + Tylenol both contain acetaminophen) can stack to toxicity.
- Always verify with the prescriber, pharmacist, or poison control (1-800-222-1222 in US) for any uncertainty.