Amoxicillin Pediatric Dosage Calculator
See the weight-based arithmetic behind published pediatric amoxicillin dosing ranges: milligrams per dose and milliliters per dose for common oral suspensions. Built for learning and double-checking understanding — not for prescribing.
Dose estimator
Enter the child's weight, pick the dosing range described in guidelines and the schedule, then the suspension strength on the bottle label. Everything is computed in your browser — nothing is sent anywhere.
Estimated result
- Regimen
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- Weight used
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- Total per day
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- Practical measure
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Educational estimate only — not a dose recommendation. This shows the arithmetic behind published dosing ranges. The actual dose must be confirmed by the child's doctor or pharmacist, and a penicillin allergy must be ruled out before any use.
Dosing reference table (q12h, per dose)
The per-dose amounts the standard arithmetic produces for common weights, shown for learning. Values marked * are capped at the commonly cited 1,000 mg per-dose maximum. Above 40 kg, pediatric references switch to adult dosing.
| Weight | Standard 45 mg/kg/day | High-dose 80 mg/kg/day | High-dose 90 mg/kg/day |
|---|---|---|---|
| 5 kg | 112.5 mg | 200 mg | 225 mg |
| 10 kg | 225 mg | 400 mg | 450 mg |
| 15 kg | 337.5 mg | 600 mg | 675 mg |
| 20 kg | 450 mg | 800 mg | 900 mg |
| 25 kg | 562.5 mg | 1,000 mg | 1,000 mg* |
| 30 kg | 675 mg | 1,000 mg* | 1,000 mg* |
| 35 kg | 787.5 mg | 1,000 mg* | 1,000 mg* |
| 40 kg | 900 mg | 1,000 mg* | 1,000 mg* |
* Capped at the commonly cited 1,000 mg per-dose maximum (some references cite 875–1,000 mg). Table is illustrative; it does not replace a prescriber's judgment.
Worked examples
Step-by-step arithmetic, exactly as the calculator performs it.
Example 1 — standard dose, 20 kg child
- Daily amount: 20 kg × 45 mg/kg = 900 mg/day
- Every 12 hours = 2 doses/day: 900 ÷ 2 = 450 mg per dose
- Suspension 250 mg/5 mL → 50 mg per mL: 450 ÷ 50 = 9 mL per dose
Example 2 — high dose, 18 kg child
- Daily amount: 18 kg × 90 mg/kg = 1,620 mg/day
- Every 12 hours = 2 doses/day: 1,620 ÷ 2 = 810 mg per dose
- Suspension 400 mg/5 mL → 80 mg per mL: 810 ÷ 80 = 10.1 mL per dose
Example 3 — weight in pounds: 44 lb child
- Convert: 44 lb ÷ 2.20462 = 19.96 kg
- Daily amount: 19.96 kg × 45 mg/kg = 898.1 mg/day
- Every 12 hours: 898.1 ÷ 2 = 449.1 mg per dose
- Suspension 250 mg/5 mL → 50 mg per mL: 449.1 ÷ 50 = 9 mL per dose
Frequently asked questions
Educational answers about the dosing ranges this calculator is based on.
How is a child's amoxicillin dose calculated from weight?
Published pediatric references commonly describe dosing as milligrams per kilogram of body weight per day (mg/kg/day), divided into 2 or 3 doses. For example, at 45 mg/kg/day given every 12 hours, a 20 kg child would be described as 20 x 45 / 2 = 450 mg per dose. This calculator follows that same arithmetic for educational purposes; it does not prescribe a dose.
What is the standard amoxicillin dose for children?
Guidelines commonly describe 40-45 mg/kg/day divided every 12 hours (or every 8 hours) for standard pediatric indications. Some references use 45 mg/kg/day as the typical standard figure. The final regimen is chosen by the child's doctor.
What is high-dose amoxicillin, and when is it described in guidelines?
High-dose amoxicillin is commonly described as 80-90 mg/kg/day divided every 12 hours, and appears in guidelines for situations such as acute otitis media or sinusitis where resistant bacteria are a concern. Whether high-dose therapy is appropriate is a decision for the prescribing doctor.
What is the maximum amoxicillin dose per dose for a child?
Many pediatric references cap a single dose at 1,000 mg for twice-daily regimens (some cite 875-1,000 mg). This calculator caps per-dose results at 1,000 mg and flags when capping occurs. Children over 40 kg are generally dosed as adults.
What happens if a child weighs more than 40 kg?
Pediatric references commonly switch to adult dosing above 40 kg: typically 500 mg every 8 hours or 875 mg every 12 hours. This calculator applies that rule automatically and labels the result as adult dosing.
How do I convert the mg dose into mL of liquid suspension?
Divide the mg per dose by the suspension's concentration in mg per mL. For a 250 mg/5 mL suspension, each mL contains 50 mg, so 450 mg / 50 = 9 mL. Always confirm the exact strength printed on your bottle with the pharmacist.
What are the common amoxicillin suspension strengths?
Commonly available strengths include 125 mg/5 mL, 200 mg/5 mL, 250 mg/5 mL, and 400 mg/5 mL. Using the wrong strength in the math is a common source of error, so this calculator asks you to pick the one printed on the label.
Is amoxicillin given every 8 hours or every 12 hours in children?
Both schedules appear in pediatric references: 2 times daily (every 12 hours) or 3 times daily (every 8 hours), depending on the indication and the prescriber's choice. High-dose regimens are most commonly described every 12 hours.
Can this calculator be used for a child's dental infection?
The weight-based arithmetic is the same regardless of indication, but dental infections in children need a dentist's diagnosis - not every tooth pain needs antibiotics, and dosing for dental use is set by the dentist. Treat this page as background education, not dental advice.
Is this calculator a substitute for a doctor's prescription?
No. Amoxicillin is a prescription medicine. This page shows the arithmetic behind published dosing ranges for education only; the actual dose, frequency, and duration must come from a doctor, dentist, or pharmacist who has seen the child.
What about penicillin allergy?
A history of penicillin allergy is a contraindication described in every major reference - a child with a known or suspected penicillin allergy must not receive amoxicillin unless a doctor specifically evaluates and directs otherwise. Always tell the prescriber and pharmacist about any drug allergy.
Does this tool cover other antibiotics or adult dosing?
No. It covers pediatric amoxicillin only. Adult dosing appears solely as the automatic rule for weights over 40 kg, and it does not estimate doses for other antibiotics such as azithromycin or cephalexin - those have entirely different dosing rules.
Scope boundary
- This tool is: an educational arithmetic estimator for pediatric amoxicillin dosing ranges described in guidelines.
- Not a prescription or diagnosis tool. Indication, allergies, kidney function, and other medicines can all change the real-world dose — only the prescriber weighs those.
- Not for other antibiotics. Azithromycin, cephalexin, and others follow entirely different dosing rules; this math does not transfer.
- Not for pets. Animal dosing is a separate matter — see our cat Benadryl dosage estimator for an example of a pet-specific tool.
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