Amoxicillin Pediatric Dosage Calculator
Enter your child's weight and select the clinical indication to get the recommended amoxicillin dose per administration, the daily total, and the volume of liquid suspension to measure. The calculator covers 7 common pediatric indications including ear infections, strep throat, pneumonia, and endocarditis prophylaxis. Switch between metric and imperial weight, and choose the suspension concentration on hand.
How amoxicillin dose is calculated for children
Unlike adult dosing which uses fixed amounts, amoxicillin doses for children are weight-based, expressed in milligrams per kilogram of body weight (mg/kg). For most common infections, the prescriber multiplies the child's weight in kilograms by the recommended mg/kg/day value for that condition, then divides the result by the number of doses per day to get the amount per administration. Maximum dose caps apply to prevent overdose in heavier children: the FDA label directs that children weighing 40 kg or more be dosed as adults, so the general oral regimen is capped at 500 mg per administration and 1,500 mg per day regardless of weight.
Dosing varies by indication, not just weight
The recommended mg/kg range differs significantly depending on the condition being treated. The FDA label puts a routine infection at 20 mg/kg/day divided every 8 hours for mild to moderate illness and 40 mg/kg/day divided every 8 hours for severe illness, whereas an ear infection caused by resistant bacteria (acute otitis media) calls for 80-90 mg/kg per day given as two divided doses. Strep throat has a unique regimen: it uses a flat dose based on weight bands rather than a per-kg calculation, given once daily for a full 10 days. Endocarditis prophylaxis before a dental or surgical procedure is a single 50 mg/kg dose given 30-60 minutes before the procedure, with a 2 g maximum. Choosing the wrong indication would result in underdosing (risking treatment failure) or overdosing (risking side effects), so the prescriber's guidance on indication is essential.
Reading the suspension label and measuring accurately
Amoxicillin for children is most often dispensed as an oral suspension (liquid). Bottles commonly come in four concentrations: 125 mg/5 mL, 200 mg/5 mL, 250 mg/5 mL, and 400 mg/5 mL. The concentration printed on the label tells you how many milligrams are in every 5 mL of liquid. To find the volume to measure, divide the dose in milligrams by the mg/mL value of the suspension. For example, if the dose is 250 mg and the suspension is 250 mg/5 mL (that is, 50 mg/mL), you need 250 / 50 = 5 mL. Always use a calibrated oral syringe or dosing cup, never a household teaspoon, because kitchen spoons hold varying volumes and can lead to significant dosing errors.
Completing the course and recognizing side effects
Amoxicillin is generally well tolerated in children. The most common side effects are gastrointestinal: nausea, vomiting, diarrhea, and abdominal discomfort. A skin rash occurs in roughly 3-5% of children, which is often not a true penicillin allergy but rather a non-allergic reaction. A hives-type rash or any breathing difficulty requires immediate medical attention. Completing the full prescribed course is critical: stopping early when the child feels better can allow the infection to return and may contribute to antibiotic resistance. Store reconstituted suspension in the refrigerator and discard any unused portion after the date stated on the label, usually 14 days.
Amoxicillin pediatric dosing by indication
| Indication | Dose | Frequency | Max daily | Typical duration |
|---|---|---|---|---|
| General infection (oral) | 40 mg/kg/day divided | Every 8 h (TID) | 1,500 mg | 7-14 days |
| General infection (IV) | 40 mg/kg/day divided | Every 8 h (TID) | 4,000 mg | 7-10 days |
| Ear infection / AOM | 80-90 mg/kg/day divided | Every 12 h (BID) | 4,000 mg | 5-10 days |
| Strep throat (<15 kg) | 50 mg/kg/day | Once daily | 750 mg | 10 days |
| Strep throat (15-29 kg) | 750 mg flat | Once daily | 750 mg | 10 days |
| Strep throat (>=30 kg) | 1,000 mg flat | Once daily | 1,000 mg | 10 days |
| Sinusitis (standard) | 45 mg/kg/day divided | Every 12 h (BID) | 4,000 mg | 5-10 days |
| Sinusitis (high-dose) | 80-90 mg/kg/day divided | Every 12 h (BID) | 4,000 mg | 7-10 days |
| UTI | 40 mg/kg/day divided | Every 8 h (TID) | 1,500 mg | 7 days |
| Endocarditis prophylaxis | 50 mg/kg single dose | Once pre-procedure | 2,000 mg | Single dose |
Guidelines based on AAP and AHA recommendations. Doses shown are typical ranges; always follow your prescriber.
Frequently asked questions
What is the standard amoxicillin dose for a child by weight?
The FDA-approved label for children over 3 months gives 20 mg/kg/day divided every 8 hours for mild to moderate infections and 40 mg/kg/day divided every 8 hours for severe infections, up to the adult maximum of 500 mg per dose and 1,500 mg per day. For ear infections (AOM), higher doses of 80-90 mg/kg/day split into two daily doses are used. The correct dose depends on the specific infection, so always follow your prescriber's instructions.
How many mL of amoxicillin suspension should I give?
Divide the prescribed dose in milligrams by the concentration of the suspension in mg/mL. If you have a 250 mg/5 mL bottle, that is 50 mg per mL. A 250 mg dose therefore needs 5 mL. A 125 mg dose from the same bottle needs 2.5 mL. This calculator computes the exact volume automatically once you enter the weight and select the suspension strength.
Why is the ear infection (AOM) dose so much higher than the general dose?
Acute otitis media (middle ear infection) is often caused by Streptococcus pneumoniae, including strains that have reduced sensitivity to amoxicillin. Reaching higher tissue concentrations in the middle ear requires using higher mg/kg doses, typically 80-90 mg/kg/day given in two divided doses so that each dose produces a high peak level. This overcomes the minimum inhibitory concentration (MIC) for these less susceptible strains and is backed by AAP (American Academy of Pediatrics) guidelines.
What is the maximum daily dose of amoxicillin for a child?
It depends on the regimen. Standard oral dosing is capped at the adult maximum of 500 mg per dose and 1,500 mg per day. High-dose regimens such as ear infection and sinusitis treatment are capped at 4,000 mg (4 g) per day. For strep throat using the once-daily regimen, the maximum per dose is 1,000 mg. For UTI it is 1,500 mg per day. For endocarditis prophylaxis it is a single 2,000 mg dose. These caps prevent toxicity in older and heavier children whose weight-based calculation would otherwise exceed a safe amount.
How long should my child take amoxicillin?
Duration depends on the infection. Strep throat requires a full 10-day course to eradicate the bacteria and prevent complications like rheumatic fever. Ear infections typically run 5-10 days depending on age and severity. UTIs are usually 7 days. Sinusitis is typically 5-10 days. Endocarditis prophylaxis is a single dose only. Never stop early just because symptoms improve, as doing so increases the risk of the infection returning and may contribute to antibiotic resistance.
Can I use this calculator if I only know my child's weight in pounds?
Yes. Select "Pounds (lb)" from the weight unit selector and enter the weight in pounds. The calculator converts it to kilograms internally before applying the mg/kg formula, then displays the results in both formats in the steps panel.
Is this calculator a substitute for a doctor's prescription?
No. This tool is for educational purposes and to help parents understand how doses are calculated. Amoxicillin requires a prescription in most countries, and the correct dose, indication, duration, and frequency must be confirmed by a licensed prescriber who has examined your child. Never administer antibiotics based solely on an online calculator.
Sources
- FDA-approved amoxicillin oral suspension label - Dosage and Administration (DailyMed)
- Shulman ST et al. IDSA Clinical Practice Guideline for Group A Streptococcal Pharyngitis (Clin Infect Dis, 2012)
- American Academy of Pediatrics: Principles of Appropriate Use for Upper Respiratory Tract Infections
- Lieberthal AS et al. AAP Clinical Practice Guideline: Management of Acute Otitis Media (Pediatrics, 2013)
- Wilson W et al. AHA Guideline: Prevention of Infective Endocarditis (Circulation, 2007)