Amoxicillin Dose Calculator

Medical safety notice: This calculator is for education and workflow review only. Amoxicillin should be prescribed by a licensed clinician after diagnosis, allergy review, renal assessment, age review, and local guideline selection.

Calculator Form

Patient name

Age

Age unit

Weight

Weight unit

Regimen

Dose interval

Severity for renal fallback

Renal category

Formulation

Course length (days)

Custom mg/kg/day

Optional max daily dose (mg)

Example Data Table

Scenario	Age	Weight	Regimen	Interval	Estimated daily total	Approximate dose
Child example	5 years	18 kg	Mild ENT	Every 12 hours	450 mg/day	225 mg per dose
Child severe example	7 years	24 kg	Severe ENT	Every 12 hours	1080 mg/day	540 mg per dose
Adult example	33 years	68 kg	Lower respiratory	Every 12 hours	1750 mg/day	875 mg per dose

Formula Used

Pediatric estimate: Daily dose = weight in kg × selected mg/kg/day. Per-dose amount = daily dose ÷ doses per day.

Adult labeled estimate: Adults and children weighing 40 kg or more use fixed schedules, commonly 250 to 500 mg every 8 hours or 500 to 875 mg every 12 hours, depending on severity and site.

Infants 3 months or less: Upper dose cap = 30 mg/kg/day, divided every 12 hours.

Renal adjustment logic: Severe renal impairment changes interval and fixed adult dose ranges. The 875 mg tablet is avoided when GFR is below 30 mL/min.

Liquid conversion: Volume in mL = mg per dose ÷ mg per mL.

How to Use This Calculator

Enter age and weight with the correct units.
Select the closest regimen and dose interval.
Choose renal status before trusting any estimate.
Pick the real product strength being dispensed.
Use the custom regimen only when a clinician already chose a mg/kg/day target.
Review the rounded dose, total course amount, and graph.
Check allergies, diagnosis, local resistance guidance, and duration separately.

Frequently Asked Questions

1. Can this calculator replace a prescription decision?

No. It estimates dosing patterns only. Final prescribing must consider diagnosis, allergies, renal function, formulation, local resistance, and patient-specific clinical factors.

2. Why does the calculator switch to adult logic at 40 kg?

The labeled product information treats children weighing 40 kg or more like adults for common oral schedules. That threshold simplifies fixed-tablet dosing.

3. Why is dosing capped for infants younger than 3 months?

Neonates and young infants clear amoxicillin more slowly. The labeled upper amount is 30 mg/kg/day divided every 12 hours.

4. Why does kidney function matter so much?

Amoxicillin is cleared mainly through the kidneys. Severe impairment usually requires longer intervals and lower fixed adult amounts to reduce accumulation risk.

5. Does the graph prove the regimen is correct?

No. The graph only visualizes the entered schedule and repeated daily totals. It does not confirm clinical appropriateness.

6. Can I use this for amoxicillin-clavulanate products?

No. Combination products have different strength conventions and clavulanate exposure limits. Use a dedicated co-amoxiclav calculator instead.

7. Why are solid doses rounded?

Tablets and capsules cannot usually match exact fractional milligram targets. Rounding helps estimate a practical administration amount, but pharmacist review is still important.

8. Should duration come only from this page?

No. Course length varies by infection type, severity, and guideline. This field mainly helps estimate total quantity for dispensing review.