Amoxicillin Dose Calculator
An expert tool for calculating pediatric amoxicillin dosage.
Please enter a valid, positive weight.
Select the daily dosage prescribed by your doctor.
Check the concentration on the medicine bottle.
Calculated single dose (mg) vs. maximum recommended single dose for this indication.
| Weight Range | Est. Daily Dose (80-90 mg/kg) | Approx. Volume per Dose (400mg/5mL, BID) |
|---|---|---|
| 8 – 12 kg | 640 – 1080 mg | 4.0 – 6.8 mL |
| 13 – 17 kg | 1040 – 1530 mg | 6.5 – 9.6 mL |
| 18 – 22 kg | 1440 – 1980 mg | 9.0 – 12.4 mL |
| 23 – 27 kg | 1840 – 2430 mg | 11.5 – 15.2 mL |
| 28 – 32 kg | 2240 – 2880 mg | 14.0 – 18.0 mL |
Example dosage table based on the high-dose (AOM) indication. This does not replace a medical prescription.
What is an Amoxicillin Dose Calculator?
An amoxicillin dose calculator is a specialized digital tool designed to help parents, caregivers, and healthcare professionals accurately determine the correct dosage of amoxicillin for children. Amoxicillin is one of the most commonly prescribed antibiotics for pediatric bacterial infections, but its dosage is not one-size-fits-all. It depends critically on the child’s body weight, the severity of the infection, and the specific concentration of the liquid suspension. This calculator simplifies the complex math involved, reducing the risk of dosing errors.
This tool is intended for anyone who needs to administer liquid amoxicillin to a child under a doctor’s supervision. It is particularly useful for parents who receive a prescription based on mg/kg/day and need to convert it into a practical measurement (in milliliters, mL). A reliable amoxicillin dose calculator provides peace of mind by translating a clinical prescription into a clear, actionable instruction. One common misconception is that this calculator can replace a doctor’s advice. It cannot. It is a tool for executing a prescription, not for diagnosing or deciding to use antibiotics. Always consult a healthcare professional before administering any medication.
Amoxicillin Dose Calculator Formula and Explanation
The calculation performed by an amoxicillin dose calculator follows a logical, multi-step process rooted in medical dosing principles. The goal is to convert a weight-based daily dosage recommendation into a specific volume of liquid medication for a single dose. The core formula is:
Volume per Dose (mL) = Single Dose (mg) / Medication Concentration (mg/mL)
To get there, the calculator first determines the following:
- Convert Weight to Kilograms (kg): If weight is entered in pounds (lbs), it is converted to kg (1 lb = 0.453592 kg). All pediatric dosing is based on kilograms.
- Calculate Total Daily Dose (mg): The child’s weight in kg is multiplied by the prescribed daily dosage in mg/kg/day. For example, a 15 kg child on a 90 mg/kg/day regimen gets 1350 mg per day.
- Calculate Single Dose (mg): The total daily dose is divided by the number of doses per day (e.g., 2 for twice a day). In our example, 1350 mg / 2 = 675 mg per single dose.
- Determine Final Volume (mL): The single dose in mg is divided by the concentration of the medication. If the pharmacy provides a 400 mg / 5 mL suspension, the concentration is 80 mg/mL. The final step is 675 mg / 80 mg/mL = 8.4 mL per dose.
Variables Table
| Variable | Meaning | Unit | Typical Range |
|---|---|---|---|
| Patient Weight | The child’s body weight. | kg or lbs | 5 – 40 kg |
| Daily Dosage | Prescribed mg of drug per kg of body weight per day. | mg/kg/day | 20 – 90 |
| Concentration | The strength of the liquid amoxicillin. | mg / 5 mL | 125, 200, 250, 400, 600 |
| Frequency | How many times the dose is given per day. | doses/day | 2 or 3 |
Practical Examples of the Amoxicillin Dose Calculator
Example 1: Toddler with a Severe Ear Infection (AOM)
A doctor diagnoses a 3-year-old child with acute otitis media (AOM) and prescribes a high-dose amoxicillin regimen.
Inputs:
- Patient Weight: 33 lbs (which the calculator converts to 15 kg)
- Indication: High Dose / AOM (90 mg/kg/day)
- Medication Strength: 400 mg / 5 mL
- Dosing Frequency: Twice a day
Calculator Outputs:
- Volume per Dose: 8.4 mL
- Total Daily Dose: 1350 mg
- Single Dose Strength: 675 mg
Interpretation: The parent should administer 8.4 mL of the 400mg/5mL amoxicillin suspension every 12 hours. Using a proper pediatric dosing guide and oral syringe is crucial for accuracy.
Example 2: School-Aged Child with Strep Throat
A 6-year-old child is diagnosed with streptococcal pharyngitis, requiring a standard dosage.
Inputs:
- Patient Weight: 22 kg
- Indication: Standard Dose (45 mg/kg/day)
- Medication Strength: 250 mg / 5 mL
- Dosing Frequency: Twice a day
Calculator Outputs:
- Volume per Dose: 9.9 mL
- Total Daily Dose: 990 mg
- Single Dose Strength: 495 mg
Interpretation: The caregiver must provide 9.9 mL of the 250mg/5mL suspension twice daily. Understanding these calculations helps in managing antibiotic dosage for children safely.
How to Use This Amoxicillin Dose Calculator
Using our amoxicillin dose calculator is straightforward. Follow these steps to ensure you get an accurate and safe result based on your doctor’s prescription.
- Enter Patient Weight: Input the child’s weight. Use the toggle to select whether you are entering the value in kilograms (kg) or pounds (lbs). The calculator will automatically handle the conversion.
- Select the Dosage Level: Choose the indication from the dropdown menu that matches the doctor’s prescription (e.g., Standard Dose, High Dose). This is based on the mg/kg/day value your doctor recommended.
- Select Medication Strength: Look at the label on the amoxicillin bottle provided by the pharmacy. Select the matching concentration from the list (e.g., 400 mg / 5 mL). This is a critical step for a correct child weight-based medication calculation.
- Choose Dosing Frequency: Select how often the medication should be administered, as per the prescription (usually twice or three times a day).
- Review the Results: The calculator instantly updates. The primary result, “Volume to Administer per Dose,” is the exact amount in mL you should draw into an oral syringe. The intermediate values show the total daily medication in mg and the strength of each single dose.
Always double-check the inputs against the prescription. The “Reset” button clears all fields to their default state, and the “Copy Results” button is useful for sharing the information with a co-parent or saving it for your records.
Key Factors That Affect Amoxicillin Dose Calculator Results
Several factors critically influence the output of an amoxicillin dose calculator. Understanding them is key to appreciating why dosage is so specific.
1. Patient’s Weight
This is the most critical factor. Pediatric medication is almost always dosed based on weight to ensure efficacy while minimizing toxicity. A heavier child requires more medication than a lighter child to achieve the same therapeutic concentration in the bloodstream.
2. Severity and Type of Infection
Different bacteria and infection sites require different levels of antibiotic to be effective. A standard skin infection might be treated with 25-45 mg/kg/day, whereas a stubborn middle ear infection (acute otitis media) often requires a high dose of 80-90 mg/kg/day to penetrate the ear fluid effectively. Your doctor determines this based on clinical guidelines. More information can be found in our fever in children guide.
3. Concentration of the Medication
Liquid amoxicillin comes in various strengths, like 125mg/5mL, 250mg/5mL, or 400mg/5mL. A higher concentration means more medicine is packed into each milliliter. Failing to select the correct concentration in the amoxicillin dose calculator is one of the most common and dangerous sources of error, leading to significant under- or over-dosing.
4. Dosing Frequency
The total daily dose can be split into two or three doses. A twice-daily (q12h) regimen will have larger individual doses than a three-times-daily (q8h) regimen, even though the total amount of drug per day is the same. This affects the volume you administer each time.
5. Renal Function (Kidney Health)
Amoxicillin is cleared from the body by the kidneys. In children with impaired renal function, the drug may not be cleared as quickly, leading to accumulation. In such cases, a doctor will prescribe a lower dose or a longer interval between doses. This calculator assumes normal kidney function.
6. Age of the Patient
While weight is primary, age is also a consideration, especially in neonates (under 3 months old). Very young infants have immature kidney function, which can delay the clearance of the drug, necessitating special dosing considerations by a pediatrician. Our growth percentile calculator can provide more context on child development.
Frequently Asked Questions (FAQ)
Give the missed dose as soon as you remember. However, if it’s almost time for the next dose, skip the missed dose and resume the regular schedule. Do not give a double dose to make up for the missed one.
Yes, you can mix the dose with formula, milk, fruit juice, water, or other cold drinks to make it more palatable. Ensure the child consumes the entire mixture immediately to get the full dose.
An accurate amoxicillin dose calculator is vital because an incorrect dose can be ineffective (if too low) or cause increased side effects (if too high). Using a verified tool ensures the prescribed regimen is followed precisely.
The most common side effects are diarrhea, nausea, and skin rash. A widespread, non-itchy rash can sometimes appear several days into treatment and is not necessarily an allergic reaction, but you should always report it to your doctor.
Reconstituted oral liquid should be stored in the refrigerator (between 2°C and 8°C). Discard any unused medicine after 14 days. Do not freeze it.
No, this amoxicillin dose calculator is specifically designed for pediatric weight-based dosing. Adult doses are typically standard (e.g., 500 mg or 875 mg) and not calculated by weight.
Children weighing 40 kg (about 88 lbs) or more are typically prescribed standard adult doses. This calculator is intended for children who still require weight-based dosing.
A higher concentration is often more convenient as it requires a smaller volume of liquid per dose, which can be easier for a child to take. However, the therapeutic effect is the same as long as the correct milligram dose is given. Always use what the pharmacy provides and what the doctor prescribed.