Amoxicillin Dosage Calculator for Children (mg/kg to mL)

How it works

daily dose (mg) = weight (kg) × mg/kg/day · each dose = daily dose ÷ doses per day (capped at the adult dose: 500 mg, 875 mg, 2,000 mg for high-dose ear infection, 1,000 mg once daily for strep) · mL = mg per dose ÷ (suspension mg ÷ 5 mL) · under 3 months: max 30 mg/kg/day in 2 doses

Amoxicillin for children is dosed by weight. The FDA label gives 25 mg/kg/day (mild–moderate) or 45 mg/kg/day (severe infections) divided every 12 hours, and at most 30 mg/kg/day for babies under 3 months; children 40 kg and over take adult doses. For ear infections the American Academy of Pediatrics recommends high-dose amoxicillin, 80–90 mg/kg/day in two doses, and for strep throat IDSA guidelines allow 50 mg/kg once daily (max 1,000 mg) for 10 days. The volume then depends on the suspension strength printed on the bottle — the same dose is twice as many mL of 200 mg/5 mL as of 400 mg/5 mL. Antibiotics are prescription-only: use this to double-check the label, not to choose a dose.

Worked example

A 15 kg child prescribed high-dose amoxicillin for an ear infection: 90 × 15 = 1,350 mg a day, split into two doses of 675 mg every 12 hours. With 400 mg/5 mL suspension (80 mg per mL), each dose is 675 ÷ 80 = 8.4 mL (675 mg). The same dose would be 16.9 mL of 200 mg/5 mL suspension.

Sources: Amoxicillin labels (FDA) — DailyMed · AAP clinical practice guideline: diagnosis and management of acute otitis media (2013) · IDSA guideline: group A streptococcal pharyngitis (2012)

Frequently asked questions