How the dose is calculated
Amoxicillin is dosed in mg/kg/day, split across the selected regimen's dosing frequency. The standard regimen covers most mild-to-moderate infections; the high-dose regimen is used where resistant Streptococcus pneumoniae is more likely (e.g. acute otitis media, sinusitis) or in higher-risk patients, per paediatric and adult prescribing guidance.
Typical dosing by indication
| Indication | Dose | Frequency | Max |
|---|---|---|---|
| Standard-dose | 40 mg/kg/day | every 8h (3×/day) | 1500 mg/day |
| High-dose | 90 mg/kg/day | every 12h (2×/day) | 4000 mg/day |
| General dosing | 30 mg/kg/day | every 8h (3×/day) | 1500 mg/day |
Amoxicillin dose chart (quick reference by weight)
Per-dose amount for each regimen at common weight bands, using a 250 mg/5 mL suspension — this dose chart mirrors the calculator above exactly; use the calculator for any weight not listed or a different suspension strength.
| Weight | Standard-dose (3×/day) | High-dose (2×/day) |
|---|---|---|
| 4 kg | 53 mg (1.1 mL) | 180 mg (3.6 mL) |
| 6 kg | 80 mg (1.6 mL) | 270 mg (5.4 mL) |
| 8 kg | 107 mg (2.1 mL) | 360 mg (7.2 mL) |
| 10 kg | 133 mg (2.7 mL) | 450 mg (9.0 mL) |
| 15 kg | 200 mg (4.0 mL) | 675 mg (13.5 mL) |
| 20 kg | 267 mg (5.3 mL) | 900 mg (18.0 mL) |
| 25 kg | 333 mg (6.7 mL) | 1000 mg (20.0 mL, capped) |
| 30 kg | 400 mg (8.0 mL) | 1000 mg (20.0 mL, capped) |
| 40 kg | 500 mg (10.0 mL, capped) | 1000 mg (20.0 mL, capped) |
| 50 kg+ / adult | 500 mg (10.0 mL, capped) | 1000 mg (20.0 mL, capped) |
H. pylori eradication therapy
Amoxicillin is a core component of Helicobacter pylori eradication regimens, always combined with a proton pump inhibitor (and usually a second antibiotic) rather than used alone — these are fixed adult combination doses, not weight-based like the calculator above.
| Regimen | Components | Duration |
|---|---|---|
| Dual therapy | Amoxicillin 1000 mg BD + lansoprazole BD | 14 days |
| Triple therapy (preferred) | Amoxicillin 1000 mg BD + clarithromycin 500 mg BD + lansoprazole 30 mg BD | 14 days |
Triple therapy is generally preferred over dual therapy for better eradication rates, but local clarithromycin resistance patterns should guide the choice — where resistance is high, an alternative (e.g. bismuth-based quadruple therapy) may be used instead.
Extended-release tablet (pharyngitis/tonsillitis)
A once-daily extended-release amoxicillin tablet formulation is approved specifically for streptococcal pharyngitis/tonsillitis, as an alternative to the standard multiple-times-daily dosing above.
| Indication | Dose | Frequency | Duration |
|---|---|---|---|
| Pharyngitis/tonsillitis (adult, extended-release tablet) | 775 mg | once daily, within 1 hour of a meal | 10 days |
Unlike the immediate-release suspension/tablet, the extended-release tablet must be taken within 1 hour of finishing a meal and swallowed whole (not chewed, crushed, or split) — food timing affects its absorption in a way the standard formulation isn't as sensitive to.
Clinical use
- Amoxicillin is first-line for many common infections — acute otitis media, community-acquired pneumonia in children, streptococcal pharyngitis, and uncomplicated UTI — because of its narrow spectrum and excellent oral bioavailability.
- High-dose regimens are preferred where drug-resistant Streptococcus pneumoniae is a concern, since higher tissue concentrations can overcome reduced penicillin-binding-protein affinity.
- Not appropriate for infections likely caused by beta-lactamase-producing organisms — amoxicillin-clavulanate (Augmentin) is used instead in that setting.
- For H. pylori eradication, amoxicillin is always part of a combination regimen with a PPI (± clarithromycin) — it is not effective as monotherapy for this indication.
- The extended-release tablet for pharyngitis/tonsillitis is a fixed 775 mg adult dose, not weight-based, and depends on being taken with food for proper absorption.
- Renal impairment requires dose-interval adjustment; confirm against local renal dosing guidance for significant CrCl reduction.
Frequently asked questions
What is the general amoxicillin dose?
30 mg/kg/day divided into 3 doses (every 8 hours) is a commonly cited general/adult dosing figure — for a typical adult this works out to the classic 500 mg three-times-daily regimen. Select "General dosing" above and enter the weight for the exact per-dose amount.
What is the amoxicillin dose for H. pylori?
As part of triple therapy (preferred): amoxicillin 1000 mg twice daily + clarithromycin 500 mg twice daily + lansoprazole 30 mg twice daily, for 14 days. As dual therapy: amoxicillin 1000 mg + lansoprazole, both twice daily, for 14 days. Amoxicillin is never used alone for H. pylori eradication.
What is the extended-release amoxicillin dose for tonsillitis/pharyngitis?
775 mg once daily, taken within 1 hour of finishing a meal, for 10 days — this is a fixed adult dose using the extended-release tablet formulation, and the tablet must be swallowed whole, not split or crushed.
Is amoxicillin dosed by weight in children?
Yes — paediatric amoxicillin dosing is calculated in mg per kg of body weight per day, then divided across the prescribed frequency, unlike the fixed adult doses used once a child reaches adult weight.
What's the difference between standard-dose and high-dose amoxicillin?
High-dose amoxicillin (around 80–90 mg/kg/day) is used when drug-resistant Streptococcus pneumoniae is more likely, such as in acute otitis media or sinusitis, or in children under 2 or with recent antibiotic exposure — it isn't needed for every infection.
Can amoxicillin be given with food?
Yes — amoxicillin absorption is not significantly affected by food, so it can be given with or without meals, which can help reduce stomach upset.
What if a dose of amoxicillin is missed?
Give the missed dose as soon as remembered unless it's almost time for the next one — in that case skip it and resume the normal schedule. Don't double up doses.
References
- Bradley JS, et al. The Management of Community-Acquired Pneumonia in Infants and Children (PIDS/IDSA). Clin Infect Dis. 2011.
- American Academy of Pediatrics. Clinical Practice Guideline: The Diagnosis and Management of Acute Otitis Media. Pediatrics. 2013.
- British National Formulary for Children (BNFc) — Amoxicillin.
- Tripathi KD. Essentials of Medical Pharmacology, 8th edition — Amoxicillin, H. pylori eradication regimens.