Educational tool · Last reviewed: March 2026
This tool provides weight-based dosing estimates for amoxicillin in paediatric patients. Dosing ranges are illustrative only.
Local formularies, resistance patterns, and indication-specific guidance may differ. Always verify with the treating clinician and local antimicrobial guidelines.
For neonates (<28 days) and infants <3 months, use neonatal-specific dosing references.
Amoxicillin is a broad-spectrum beta-lactam antibiotic and one of the most commonly prescribed oral antibiotics worldwide. It is active against a wide range of gram-positive and selected gram-negative bacteria and remains the first-line treatment for many community-acquired infections.
Its clinical indications include upper and lower respiratory tract infections, otitis media, community-acquired pneumonia, urinary tract infections, dental infections, and H. pylori eradication (in combination with other agents). The dose varies substantially between indications and patient populations.
Accurate weight-based dosing is particularly critical in children and in patients with renal impairment, where standard adult doses may be too high or inappropriately applied.
Enter the patient's weight (in kg, g, or lb), age, and dosing strategy — standard (25 mg/kg/day), high-dose for resistant organisms (45 mg/kg/day), or a custom mg/kg/day value. Select the dosing interval (BID, TID, or QID), and choose the target formulation (syrup or tablet).
The calculator returns the per-dose amount in mg, the daily total, the mL of syrup per dose, and the number of tablets per dose — giving a complete, ready-to-prescribe result without manual conversion.
A daily dose cap of 3,000 mg/day is applied as an educational ceiling, reflecting the standard adult maximum for most indications. The per-dose ceiling aligns with this: 500 mg per dose on TID, or 750 mg per dose on BID for high-dose regimens.
Inline warnings appear when: the child is under 3 months (amoxicillin use in this age group requires specialist guidance); the calculated dose approaches or reaches the adult ceiling (capping is applied); or a renal impairment flag is expected but not yet implemented in the current version.
Standard dosing (20–50 mg/kg/day, typically 25 mg/kg/day) divided into 2–3 doses covers the majority of amoxicillin indications. BID dosing (every 12 hours) is increasingly favoured for adherence in children. TID dosing (every 8 hours) provides more uniform serum levels and is recommended for more severe infections.
High-dose amoxicillin (45 mg/kg/day) is recommended in areas with intermediate resistance among Streptococcus pneumoniae for otitis media and sinusitis. At this dose, BID dosing achieves adequate pharmacodynamic target attainment for resistant organisms that standard dosing would miss.
Custom dosing allows entry of any mg/kg/day value for off-guideline indications or specialist protocols, such as the higher doses used in pneumococcal prophylaxis in asplenic patients or endocarditis prophylaxis.
The calculator follows a three-step process from weight and dosing strategy to the final per-dose volume:
Amoxicillin is renally excreted and accumulates in renal impairment. Standard doses may cause neurological toxicity (including seizures) when GFR falls significantly.
As a general guide: GFR 10–30 mL/min/1.73m² — extend the interval (BID to TID becomes less appropriate; consider BID with reduced dose); GFR <10 mL/min/1.73m² — significant dose reduction required, typically 250–500 mg every 24–48 hours. Haemodialysis patients require post-dialysis supplementary dosing.
The calculator does not automatically adjust for renal impairment. Renal dose modifications must be applied manually using an authoritative reference such as the Renal Drug Handbook or local institutional guidelines.
Calculated daily and per-dose amounts for standard (25 mg/kg/day) and high-dose (45 mg/kg/day) strategies, capped at 3,000 mg/day. Volume shown for 250 mg/5 mL syrup.
| Weight (kg) | Daily 25 mg/kg (mg) | Per dose TID (mg) | Daily 45 mg/kg (mg) | Per dose BID (mg) | Syrup 250 mg/5 mL — TID dose (mL) |
|---|---|---|---|---|---|
| 5 kg | 125 mg | 41.7 mg | 225 mg | 112.5 mg | 0.8 mL |
| 8 kg | 200 mg | 66.7 mg | 360 mg | 180 mg | 1.3 mL |
| 10 kg | 250 mg | 83.3 mg | 450 mg | 225 mg | 1.7 mL |
| 12 kg | 300 mg | 100 mg | 540 mg | 270 mg | 2 mL |
| 15 kg | 375 mg | 125 mg | 675 mg | 337.5 mg | 2.5 mL |
| 20 kg | 500 mg | 166.7 mg | 900 mg | 450 mg | 3.3 mL |
| 25 kg | 625 mg | 208.3 mg | 1125 mg | 562.5 mg | 4.2 mL |
| 30 kg | 750 mg | 250 mg | 1350 mg | 675 mg | 5 mL |
| 40 kg | 1000 mg | 333.3 mg | 1800 mg | 875 mg | 6.7 mL |
| 50 kg | 1250 mg | 416.7 mg | 2250 mg | 875 mg | 8.3 mL |
| 60 kg | 1500 mg | 500 mg | 2700 mg | 875 mg | 10 mL |
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Usman Shaoukat is the founder and editor of BestMedCal. He is a computer and web specialist who researches every BestMedCal tool from published standards and medication-safety references, including NIST, the U.S. FDA, NCBI and the American Academy of Pediatrics. His focus is dose-to-volume calculations and unit conversions. Every formula and worked example is checked against the sources listed on each page. BestMedCal has no clinicians on staff: our tools check arithmetic and explain methods; they do not recommend doses. If you spot an error, contact us and we will review it.