Amoxicillin Dosage Calculator for Pediatrics

Amoxicillin Dosage Calculator

Age (Years)

Age (Months)

Weight

Infection Type

Infection Severity

Mild/Moderate Severe

Recommended Dosage

Regimen	Dosage
Enter patient details to calculate dosage

Important Disclaimer: This calculator provides general dosage information only and should not be considered as medical advice. Always consult with a qualified healthcare professional before administering any medication. Dosage may vary based on the specific infection being treated, patient medical history, and other factors. The creators of this calculator are not responsible for any errors or omissions, or for any outcomes related to the use of this information.

Medically Reviewed By

Adesh Pundir, RPh – Licensed Pharmacist since 2013
Verified for accuracy and clinical relevance.
Serving patients in Fort Worth, Texas with expertise in community pharmacy and medication safety.

Last reviewed: April 2026

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How to Use Our Amoxicillin Dosage Calculator

Enter Patient Details: Select the child’s age using both the year and month dropdowns (from 1 month up to 17 years 11 months)
Input their weight in either kg or lbs using the number field and unit selector
Select Infection Type: Choose the infection location from the dropdown (Ear/Nose/Throat, Skin, Genitourinary Tract, or Lower Respiratory Tract)
Mark whether it’s a Mild/Moderate or Severe infection using the radio buttons
View Results in real-time: The calculator instantly displays recommended dosages in the right panel (or bottom on mobile)

You’ll see both twice-daily and thrice-daily dosing options

Consult Your Doctor: Review the calculated dosage regimens. Always verify with a healthcare provider before administering medication

The calculator adjusts recommendations based on: weight (under/over 40kg), infection type, and severity. For infants under 3 months, it advises direct consultation with a pediatrician.

How to Calculate Amoxicillin Dosage for Pediatrics (3 month old or less)?

Question: What is the recommended daily dosage of Amoxicillin for a 3-month-old child weighing 5 kilograms (11 lbs), following the standard dosage guideline of 30mg/kg/day?

Answer: Given:

Age of the child: 3 months
Weight of the child: 5 kilograms
Standard dosage: 30mg/kg/day

First, let’s calculate the total dosage for a day:

Calculate the Total Dosage: Total Dosage = Weight of the child (in kg) × Dosage per kg (in mg/kg/day)
Total Dosage = 5 kg × 30 mg/kg/day
Total Dosage = 150 mg/day

So, the total recommended daily dosage of Amoxicillin for the 3-month-old child weighing 5 kilograms is 150 milligrams.

Now, let’s break down the dosage frequency based on the standard guideline of dividing the total daily dosage into multiple doses.

Determine Dosage Frequency:
- Since the total dosage needs to be divided evenly over the day, let’s consider dividing it into two doses.
- The standard dosage frequency for infants is typically every 12 hours.
Therefore, the recommended dosage regimen would be to administer 75 milligrams of Amoxicillin every 12 hours.

In summary:

Total recommended daily dosage: 150 milligrams
Dosage frequency: 75 milligrams every 12 hours

Amoxicillin Dosage Chart by Weight (Pediatric)

Educational Reference: This chart uses a common pediatric dose of 45 mg/kg/day (moderate infections) and is intended as a quick reference. Actual dosing depends on the infection type, age, kidney function, and prescriber’s instructions.

Weight (kg)	Weight (lbs)	Recommended Daily Dosage (45 mg/kg/day)
5 kg	11 lbs	225 mg/day
7 kg	15 lbs	315 mg/day
9 kg	20 lbs	405 mg/day
11 kg	24 lbs	495 mg/day
14 kg	30 lbs	630 mg/day
16 kg	35 lbs	720 mg/day
18 kg	40 lbs	810 mg/day
20 kg	44 lbs	900 mg/day
23 kg	50 lbs	1,035 mg/day
25 kg	55 lbs	1,125 mg/day
27 kg	60 lbs	1,215 mg/day
30 kg	66 lbs	1,350 mg/day
32 kg	70 lbs	1,440 mg/day
34 kg	75 lbs	1,530 mg/day
36 kg	80 lbs	1,620 mg/day
39 kg	85 lbs	1,755 mg/day
40 kg	88 lbs	1,800 mg/day

How to Calculate Amoxicillin Dosage for a child more than 3 months old but weight not exceeding 40 Kg or 88lbs?

Question: What is the recommended daily dosage of Amoxicillin for a 10-year-old patient weighing 39 kilograms, using the guideline of 20 mg/kg/day by mouth every 8 hours or 25 mg/kg/day every 12 hours? Max dose not to exceed 750 mg/day.

Answer:

Determine the Maximum Daily Dosage Limit: As per the guideline, the maximum daily dosage limit is 750 mg.
Calculate the Maximum Daily Dosage Based on Weight: We’ll first calculate the maximum dosage based on the weight of the patient. According to the guideline, the maximum dosage is 20 mg/kg/day or 25 mg/kg/day.
- For 20 mg/kg/day: Maximum Dosage = Weight (kg) × 20 mg/kg/day = 39 kg × 20 mg/kg/day = 780 mg/day
- For 25 mg/kg/day: Maximum Dosage = Weight (kg) × 25 mg/kg/day = 39 kg × 25 mg/kg/day = 975 mg/day
Select the Appropriate Dosage: Since the maximum dosage based on weight exceeds the maximum daily dosage limit of 750 mg/day, we’ll choose the lower dosage option to ensure it does not exceed the limit.
- The appropriate dosage would be 20 mg/kg/day.

Calculate the Dosage Frequency: The dosage should be administered every 8 hours. To calculate the dosage for each administration, we divide the daily dosage by the number of administrations.
- Dosage per Administration = Daily Dosage / Number of Administrations per Day = 780 mg / 3 administrations ≈ 260 mg per administration

Final Recommendation: Based on the calculation, the recommended dosage of Amoxicillin for the 10-year-old patient weighing 39 kilograms would be approximately 260 mg by mouth every 8 hours.

In summary, the recommended dosage of Amoxicillin is calculated based on the patient’s weight, ensuring it does not exceed the maximum daily dosage limit. The dosage is then divided to determine the appropriate dosage frequency, as per the guideline provided.

Total recommended daily dosage: 250 milligrams divided every 8 hours or 375 milligrams divided every 12 hours

Amoxicillin Dosage Decision Tree

This Amoxicillin Dosage Decision Tree helps you choose the right dosing method based on a child’s age and weight. Babies younger than 3 months usually receive 30 mg/kg/day. For children under 40 kg, doctors calculate the dose using body weight (mg/kg/day). Patients who weigh 40 kg or more often receive the standard adult amoxicillin dose, depending on the infection. This simple guide explains the first steps in amoxicillin dosage calculation and supports safe prescribing.

How to Calculate Amoxicillin Dosage for a 15 year old patient weighing 80kg?

Question: What is the recommended daily dosage of Amoxicillin for a 15-year-old patient weighing 80 kilograms, using the guideline of 250 mg every 8 hours, or 500 mg every 12 hours Max dose not to exceed 2gram/day or 2,000mg/day.

Answer:

To calculate the appropriate dosage of Amoxicillin for a 15-year-old patient weighing 80 kilograms, we will use the guideline of 250 mg every 8 hours, or 500 mg every 12 hours. Additionally, we need to ensure that the maximum dose does not exceed 2,000 mg per day.First, let’s calculate the total daily dosage allowed:
- 250 mg every 8 hours = 3 doses per day, totaling 750 mg/day
- 500 mg every 12 hours = 2 doses per day, totaling 1000 mg/day
The maximum daily dose allowed is 2000 mg/day.
Given that the patient’s weight is 80 kilograms, we need to calculate the mg/kg/day dosage to ensure it is within safe limits.
Both calculated dosages fall within safe limits as they are below the maximum recommended dose of 20 mg/kg/day. However, we need to ensure that the total daily dosage does not exceed 2000 mg/day.
Since the total daily dosage for the 500 mg every 12 hours option is 1000 mg/day, and it is already less than 2000 mg/day, we can safely choose this option.
Therefore, the recommended dosage for the 15-year-old patient weighing 80 kilograms is 500 mg of Amoxicillin every 12 hours.

Amoxicillin Available Dosages

Amoxicillin Suspensions

-Amoxicillin 125mg/5ml
-Amoxicillin 200mg/5ml
-Amoxicillin 250mg/5ml
-Amoxicillin 400mg/5ml

Amoxicillin Tablets

-Amoxicillin 500mg Tab
-Amoxicillin 875mg Tab

Amoxicillin Capsules

-Amoxicillin 250mg Cap
-Amoxicillin 500mg Cap

Amoxicillin Chewable Tab

-Amoxicillin 125mg Tab
-Amoxicillin 250mg Tab

Amoxicillin Dosage for Different Health Conditions

Ear, Nose, and Throat Infections

Adults: 250 mg every 8 hours or 500 mg every 12 hours for mild to moderate infections. For severe infections, 500 mg every 8 hours or 875 mg every 12 hours.
Children (Sinusitis): Dose varies with age and weight, with specific recommendations for infants 3 months or younger and those older than 4 months.

Urinary Tract Infections (UTI)

Adults: For mild to moderate infection, 250 mg every 8 hours or 500 mg every 12 hours. For severe infections, 500 mg every 8 hours or 875 mg every 12 hours.
Children: Up to 30 mg/kg/day in divided doses every 12 hours for 3 months or younger. Older children’s doses vary with severity and weight.

Skin Infections

Adults: 250 mg every 8 hours or 500 mg every 12 hours for mild to moderate infections, and 500 mg every 8 hours or 875 mg every 12 hours for severe infections.
Children: Similar dosing strategy as adults, adjusted for weight and age.

Strep Throat

Adults: For tonsillitis/pharyngitis, 775 mg once a day for 10 days if using extended-release, or 1000 mg once a day or 500 mg twice a day for immediate-release.
Children’s doses vary, so it’s crucial to consult a healthcare provider.

Acute Otitis Media

Adults: 250 to 500 mg three times a day for 10 to 14 days, or 500 to 875 mg twice a day.

Pediatric Dose for Bacterial Endocarditis Prophylaxis

50 mg/kg orally as a single dose 30 to 60 minutes before the procedure, with a maximum of 2 g/dose.

Anthrax Prophylaxis

Adults: 1 g every 8 hours for 60 days as an alternative oral regimen for postexposure prophylaxis and cutaneous anthrax without systemic involvement.

Pneumonia

Mild, moderate, or severe infection: 500 mg orally every 8 hours or 875 mg every 12 hours

Tonsillitis/Pharyngitis

Extended-release: 775 mg orally once a day within 1 hour after a meal for 10 days

Frequently Asked Questions (FAQs)

1. How is amoxicillin dosage calculated?

Amoxicillin dosage is usually calculated using the patient’s body weight in kilograms (kg). Many pediatric infections use a dose based on mg/kg/day, which is then divided into two or three doses. The exact amount depends on the type and severity of the infection and should always follow your healthcare provider’s instructions.

2. What is the usual pediatric amoxicillin dosage?

The usual pediatric amoxicillin dosage ranges from 20 to 90 mg/kg/day, depending on the infection being treated. Mild infections generally require lower doses, while severe infections such as acute otitis media may require higher doses. A doctor will determine the correct dose for each child.

3. How do you calculate amoxicillin dosage by weight?

To calculate amoxicillin dosage by weight, multiply the child’s weight in kilograms by the recommended mg/kg/day dose. The total daily dose is then divided into two (BID) or three (TID) equal doses based on the prescribed treatment plan.

4. What if my child’s weight is in pounds instead of kilograms?

If your child’s weight is in pounds, divide the weight by 2.2 to convert it to kilograms. Using kilograms provides a more accurate amoxicillin dosage calculation and helps reduce dosing errors.

5. What is the maximum daily dose of amoxicillin?

The maximum daily dose depends on the patient’s age, infection, and medical condition. Healthcare providers follow established treatment guidelines and individual patient needs when determining the highest safe dose. Never increase the dose without medical advice.

6. How many times a day should amoxicillin be taken?

Amoxicillin is commonly prescribed two times daily (every 12 hours) or three times daily (every 8 hours). Your doctor will choose the dosing schedule based on the infection, the medication strength, and the patient’s age.

7. How do I measure liquid amoxicillin correctly?

Always use an oral syringe or the measuring device provided with the medicine. Avoid using household teaspoons because they are not accurate and may result in giving too much or too little medication.

8. When do children receive adult amoxicillin doses?

Children who weigh approximately 40 kg (88 pounds) or more may receive adult dosing for many infections. The final dose still depends on the infection type, kidney function, and the prescribing healthcare provider.

9. Can I use an online amoxicillin dosage calculator?

An online amoxicillin dosage calculator can quickly estimate a weight-based dose for educational purposes. However, it should never replace professional medical advice. Always confirm the final dosage with your physician or pharmacist before giving the medication.

10. Why is weight-based dosing important for amoxicillin?

Weight-based dosing helps ensure that children receive the correct amount of medicine for effective treatment while reducing the risk of underdosing or overdosing. Accurate dosing improves treatment outcomes and supports safe antibiotic use.

Amoxicillin Dosage Calculator for Pediatrics