How Pediatric Amoxicillin Dosing Is Calculated
Amoxicillin is dosed in children by body weight, in milligrams per kilogram per day (mg/kg/day), rather than as a single fixed amount. This calculator multiplies your child's weight by a standard published mg/kg/day range, splits the result across the number of doses given per day, and caps the total at the typical adult ceiling dose. It is an educational reference tool, not a prescribing tool — the dose your child actually receives should always come from their pediatrician or pharmacist.
How the calculation works
First, weight is converted to kilograms if entered in pounds (1 kg = 2.20462 lb). The total daily dose range is then weight (kg) x mg/kg/day, using either the standard-dose range (25-45 mg/kg/day) or the high-dose range (80-90 mg/kg/day) you select. That daily total is divided by the number of doses per day (2 for every-12-hours dosing, 3 for every-8-hours dosing) to get the amount per administration. If the weight-based total would exceed the typical adult maximum for that regimen, the calculator caps it there instead of continuing to scale linearly with weight.
Standard-dose vs. high-dose regimens
The standard regimen (25-45 mg/kg/day, divided every 8 or 12 hours) is the conventional choice for mild-to-moderate infections such as streptococcal pharyngitis. The high-dose regimen (80-90 mg/kg/day, divided every 12 hours) is the regimen preferred by the American Academy of Pediatrics for acute otitis media and sinusitis in regions where drug-resistant Streptococcus pneumoniae is common, because it achieves higher, more sustained drug levels. The correct regimen depends on the specific infection, local resistance patterns, and the prescriber's judgment — this tool cannot determine which regimen applies to your child.
Maximum dose and important safety notes
Once a child's weight-based dose would exceed roughly 1750 mg/day (standard-dose regimens) or 4000 mg/day (high-dose regimens) -- doses comparable to typical adult ceilings -- clinicians generally stop scaling the dose with weight and cap it at that maximum. Dosing conventions also differ for infants under about 3 months of age, and this calculator is not intended for neonatal dosing. This tool provides an educational estimate only; it does not know your child's diagnosis, kidney function, allergies, or the actual liquid concentration or tablet size prescribed. Always confirm the dose, formulation, and schedule against the prescription label and with a pharmacist or physician before giving any medication.