Amoxicillin Pediatric Dosage Calculator
Medical Disclaimer
This calculator is for educational reference only and does not replace clinical judgment. Always verify dosing with a licensed prescriber, pharmacist, or current clinical guidelines. Never adjust a child's medication without professional guidance.
Amoxicillin Pediatric Dosage Calculator
Children ≥40 kg typically receive adult dosing — see advisory in results
Select the liquid suspension strength dispensed by the pharmacy
Used to generate the daily dosing schedule
Enter Patient Details
Enter the child's weight, age, and indication above to calculate the appropriate amoxicillin dose, volume in mL, and dosing schedule.
Important
This calculator is provided for general information only and is not medical advice, diagnosis, or treatment. Results are estimates based on population averages and cannot account for your individual circumstances. Speak to a qualified healthcare professional before acting on anything you read here.
Weight-based amoxicillin dosing for children by indication
Amoxicillin is one of the most widely prescribed antibiotics for children worldwide, used to treat a broad range of bacterial infections including ear infections, strep throat, pneumonia, urinary tract infections, sinusitis, and more. Because children's bodies differ so dramatically in size and metabolic rate from adults, amoxicillin dosing in pediatrics is always weight-based — calculated in milligrams per kilogram of body weight per day (mg/kg/day) — and then divided into multiple daily doses depending on the target infection. The Amoxicillin Pediatric Dosage Calculator on EverydayTools.io gives parents, caregivers, pharmacists, medical students, and clinical practitioners a fast, evidence-based reference for checking weight-appropriate amoxicillin doses across 14 clinical indications. By entering the child's weight, age, and the indication being treated, the calculator returns the total daily dose range in milligrams, the individual dose in milligrams per administration, the recommended frequency (once daily, twice daily, or three times daily), and — critically — the volume in milliliters for the most common oral suspension concentrations. It also generates a dosing schedule based on the first-dose time the user enters, so caregivers know exactly when to give each dose throughout the day. One of the most important concepts in pediatric amoxicillin therapy is the distinction between standard dosing and high-dose dosing, particularly for acute otitis media (ear infection). With increasing rates of penicillin-resistant Streptococcus pneumoniae in many communities, standard-dose amoxicillin (40–45 mg/kg/day) may be inadequate to achieve sufficient drug levels in middle ear fluid. The American Academy of Pediatrics therefore recommends high-dose amoxicillin (80–90 mg/kg/day, maximum 4,000 mg/day) as first-line therapy for most children with ear infections in the United States. This calculator supports both dosing strategies. Suspension strength selection is another area where the calculator adds real clinical value. Amoxicillin oral suspensions come in four concentrations: 125 mg/5mL, 200 mg/5mL, 250 mg/5mL, and 400 mg/5mL. The volume required per dose differs significantly across these formulations — and administering the wrong volume could mean under- or over-dosing your child. For example, a 20 kg child on high-dose AOM therapy needs approximately 9 mL per dose with the 250 mg/5mL suspension, but only 5.5 mL with the 400 mg/5mL suspension. The calculator displays volumes for all four formulations simultaneously, helping clinicians and pharmacists choose the most practical option. The 400 mg/5mL strength is generally preferred for children two years and older because the smaller volume tends to improve compliance. Safety guardrails built into the calculator include automatic maximum dose capping per indication, a color-coded status flag (green for therapeutic range, yellow for capped at maximum, orange for potentially sub-therapeutic, red for supratherapeutic), a neonatal gate that warns users when age is under one month (where specialist guidance is always required), and an advisory for patients at or above 40 kg who typically receive adult rather than weight-based dosing. The calculator also generates a treatment course volume estimate — how many total milliliters of reconstituted suspension will be consumed over the complete antibiotic course. This helps parents and pharmacists select the right bottle size and understand why dispensing the full course matters. Completing the entire antibiotic course, even when the child feels better, is especially important for strep throat, where stopping early increases the risk of acute rheumatic fever. All dosing data in this calculator is derived from guidelines published by the American Academy of Pediatrics (AAP), the Infectious Diseases Society of America (IDSA), the World Health Organization (WHO) model formulary for children, and FDA prescribing information for amoxicillin. This tool is intended as a clinical reference and educational aid. All dosing decisions for an individual patient must be made by a qualified healthcare professional.
Understanding Pediatric Amoxicillin Dosing
What Is Amoxicillin and When Is It Used in Children?
Amoxicillin is a semi-synthetic aminopenicillin antibiotic that belongs to the beta-lactam class of drugs. It kills bacteria by inhibiting cell wall synthesis — specifically by binding to penicillin-binding proteins (PBPs), enzymes that bacteria need to build and maintain their outer walls. Without intact cell walls, bacteria lyse and die. Amoxicillin is effective against many common gram-positive organisms (Streptococcus pyogenes, Streptococcus pneumoniae, Enterococcus) and some gram-negative organisms (Haemophilus influenzae, E. coli, Helicobacter pylori). In children, it is commonly prescribed for acute otitis media (middle ear infections), group A streptococcal pharyngitis (strep throat), community-acquired pneumonia, urinary tract infections, acute bacterial sinusitis, dental and endocarditis prophylaxis, early Lyme disease in children under 8 years, and mild-to-moderate skin and skin structure infections. Amoxicillin has excellent oral bioavailability (~80%), meaning a high proportion of the oral dose reaches the bloodstream, making it highly effective as an oral antibiotic for outpatient pediatric infections.
How Is the Dose Calculated?
Pediatric amoxicillin dosing is always weight-based. The core formula is: Total Daily Dose (mg) = Child's Weight (kg) × mg/kg/day for the indication. The total daily dose is then divided by the number of daily administrations based on the prescribed frequency: once daily (qD), twice daily (BID = every 12 hours), or three times daily (TID = every 8 hours). For example, a 15 kg child with a high-dose AOM indication at 80–90 mg/kg/day would have a total daily dose of 1,200–1,350 mg. Divided by 2 for BID dosing, that is 600–675 mg per dose. Each indication has a maximum daily dose cap — if the weight-based calculation exceeds this cap, the dose is clamped at the maximum. For oral suspensions, the per-dose milligrams are converted to milliliters using: mL per dose = (mg per dose ÷ mg/mL concentration) × 5, then rounded to the nearest 0.25 mL for practical administration with an oral syringe.
Why Does Getting the Dose Right Matter?
Under-dosing amoxicillin creates two serious problems: treatment failure — the infection persists or worsens because drug levels at the site of infection never reach the minimum inhibitory concentration (MIC) required to kill the bacteria — and antibiotic resistance, as sub-inhibitory drug exposure can select for resistant bacterial mutants. Over-dosing risks gastrointestinal side effects (nausea, diarrhea, abdominal pain) and, in severe cases, crystalluria or neurotoxicity, though these are uncommon at typical oral doses. The distinction between high-dose and standard-dose amoxicillin for AOM is clinically crucial: children with high-dose therapy achieve middle ear fluid concentrations 3–4 times higher, sufficient to overcome intermediate penicillin resistance in S. pneumoniae, the most common cause of bacterial ear infections. Children at greatest risk for resistant organisms — those under 2 years, those in daycare, those recently treated with antibiotics — are most likely to benefit from high-dose therapy.
Limitations and When to Seek Professional Guidance
This calculator provides guideline-based reference dosing and should never replace a prescriber's clinical assessment. Important limitations include: (1) Renal or hepatic impairment — children with kidney disease may need dose reduction; this calculator does not adjust for renal function. (2) Drug interactions — concurrent probenecid increases amoxicillin serum levels; allopurinol increases risk of rash. (3) Allergic history — approximately 1–10% cross-reactivity exists between amoxicillin and cephalosporins in patients with penicillin allergy; always screen carefully. (4) Mononucleosis — amoxicillin causes a non-allergic maculopapular rash in approximately 80% of patients with active Epstein-Barr virus (EBV) infection; if mono is suspected, amoxicillin should be avoided. (5) Neonates under one month of age — pharmacokinetics differ significantly; specialist guidance is mandatory. (6) Resistance patterns vary by geography — local epidemiology should guide therapy. Always consult a licensed prescriber, pharmacist, or up-to-date clinical guidelines before administering any medication to a child.
How to Use This Calculator
Enter Weight and Age
Type the child's weight in kilograms or pounds — the calculator converts automatically. Enter the child's age in weeks, months, or years. Age is used to check indication-specific age constraints (e.g., AOM high-dose requires ≥2 months, CAP requires ≥3 months).
Select the Indication
Choose the condition being treated from the dropdown. For ear infections, choose between high-dose (80–90 mg/kg/day, recommended for most children) and standard-dose (40–45 mg/kg/day). For sinusitis, choose between standard and high-dose. For strep throat, choose BID or once-daily dosing.
Choose Suspension Strength and First Dose Time
Select the liquid suspension concentration dispensed by the pharmacy (125, 200, 250, or 400 mg per 5 mL). The 400 mg/5 mL formulation is preferred for children 2 years and older as it requires a smaller volume. Enter the time of the first dose to generate a full day's dosing schedule.
Review Results and Take Action
The calculator displays the dose range in mg, mL volume per dose, dosing schedule, multi-formulation comparison, and treatment course volume. Review the safety status badge and clinical notes. Always confirm with a prescriber or pharmacist before administering. Print or export the results to share with a healthcare provider.
Frequently Asked Questions
What is the standard amoxicillin dose for children with ear infections?
There are two accepted dosing strategies for acute otitis media (ear infections) in children. Standard dose is 40–45 mg/kg/day given three times daily (every 8 hours), with a maximum of 3,000 mg per day. High dose is 80–90 mg/kg/day given twice or three times daily, with a maximum of 4,000 mg per day. The American Academy of Pediatrics (AAP) recommends high-dose amoxicillin as first-line therapy for most children because it is more effective against penicillin-intermediate Streptococcus pneumoniae, the most common bacterial cause of ear infections. High-dose therapy is especially important for children under 2, those attending daycare, or those who have received an antibiotic in the past 30 days. Always follow your prescriber's specific recommendation.
Why does amoxicillin dose vary by the type of infection?
Different bacterial infections require different drug concentrations at the site of infection to effectively kill the bacteria. Ear and sinus infections require high doses because the middle ear fluid has a barrier effect that limits drug penetration, and the most common causative organisms show increasing antibiotic resistance. Community-acquired pneumonia also uses high-dose amoxicillin (90 mg/kg/day) for the same reason — achieving adequate lung tissue concentrations. In contrast, urinary tract infections can be treated with lower doses (25–50 mg/kg/day) because amoxicillin concentrates in urine and achieves very high local levels even at moderate systemic doses. Strep throat uses 50 mg/kg/day because Streptococcus pyogenes remains reliably penicillin-susceptible worldwide. The maximum daily dose also varies by indication to prevent toxicity while ensuring efficacy.
How do I choose between the amoxicillin suspension concentrations?
Amoxicillin oral suspension comes in four concentrations: 125 mg/5 mL (weakest, largest volume per dose), 200 mg/5 mL, 250 mg/5 mL (most commonly stocked), and 400 mg/5 mL (strongest, smallest volume per dose). For infants and young children below 2 years, the lower concentrations may be easier to administer. For children 2 years and older, the 400 mg/5 mL formulation is generally preferred because the smaller volume per dose is easier to get a child to swallow, improves compliance, and finishes the course before the reconstituted suspension expires (14 days refrigerated). This calculator shows the mL dose for all four concentrations simultaneously so you can compare and pick the most practical option for your specific situation.
What does it mean if the dose is capped at the maximum?
A yellow 'capped' status badge appears when the weight-based calculation (weight in kg × mg/kg/day) produces a total daily dose that exceeds the maximum guideline ceiling for that indication. For example, a 50 kg child on high-dose AOM therapy would calculate to 50 × 90 = 4,500 mg/day, which exceeds the 4,000 mg/day maximum. The calculator automatically caps the dose at 4,000 mg/day. Dose capping is important for patient safety — exceeding established maximums increases the risk of adverse effects without providing additional clinical benefit. It also reflects the shift to adult dosing once a child reaches adult body weight (approximately 40 kg). If you see the capped badge, confirm with the prescriber whether adult dosing guidelines should apply instead.
Why must the full 10-day course of amoxicillin be completed for strep throat?
Streptococcal pharyngitis (strep throat) caused by Group A Streptococcus (Streptococcus pyogenes) must be treated for the full 10 days because premature discontinuation — even after symptoms completely resolve — carries a risk of developing acute rheumatic fever, a serious inflammatory disease that can cause permanent heart valve damage (rheumatic heart disease). Strep bacteria can persist in the throat at sub-symptomatic levels after symptoms resolve, and a full 10-day antibiotic course is required to eradicate the organism reliably. This is one situation where the guideline recommendation is absolute rather than flexible. Studies have shown that shorter courses of amoxicillin (5 days) have lower eradication rates for strep throat compared to the full 10-day course. Emphasize this to parents when prescribing.
What is the mononucleosis rash warning with amoxicillin?
If a child has active Epstein-Barr virus (EBV) infection — infectious mononucleosis (mono) — and receives amoxicillin, approximately 80% will develop a distinctive, widespread, non-allergic maculopapular (flat, red, blotchy) rash within days of starting the antibiotic. This rash is not a true allergic reaction; it is an immune-mediated reaction specific to penicillin-type antibiotics in the setting of active EBV infection. The rash typically begins on the trunk and spreads to the extremities, and it fades on its own. Unfortunately, this rash is frequently mistaken for a penicillin allergy, leading to unnecessary lifelong avoidance of an important antibiotic class. Before starting amoxicillin in a teenager or child with pharyngitis, consider whether mononucleosis is a possibility (look for severe sore throat, marked fatigue, posterior cervical lymphadenopathy, splenomegaly) and test if clinically indicated.