Medication Dosage Calculator

The Medication Dosage Calculator estimates weight-based medication doses for common clinical scenarios using standard dosing guidelines. This tool is designed for educational purposes and to assist healthcare students, caregivers, and patients in understanding how doses are calculated — it is not a substitute for prescriber instructions or clinical judgment. Always confirm dosing with a licensed pharmacist or physician before administering any medication.

How to Use This Calculator

1. Enter the patient's weight in kilograms (pediatric dosing is almost always weight-based).
2. Enter the prescribed dose in mg/kg as indicated by the prescriber or guideline.
3. Enter the available concentration (mg/mL for liquid medications, or mg per tablet for solids).
4. Click Calculate to see the total dose in milligrams and the volume or number of tablets to administer.

What This Calculator Measures

This calculator computes total dose (mg) and volume or quantity to administer.

• Weight-based dose (mg/kg): Standard approach for pediatric and some adult medications.
• Total dose (mg): Patient weight × dose per kg.
• Volume to administer (mL): Total dose ÷ concentration (mg/mL) for liquid formulations.
• Tablets to administer: Total dose ÷ tablet strength, noting that splitting or rounding may be required.

Formula or Logic

Total dose (mg) = Patient weight (kg) × prescribed dose (mg/kg). Volume (mL) = Total dose (mg) ÷ concentration (mg/mL). Tablet count = Total dose (mg) ÷ tablet strength (mg). Doses should be rounded to the nearest practical unit and checked against maximum dose limits specified in the prescribing information.

Example Calculations

Example 1: Child weighing 20 kg, prescribed amoxicillin at 25 mg/kg, available as 250 mg/5 mL suspension. Total dose = 500 mg. Volume = 500 ÷ 50 = 10 mL per dose.

Example 2: Adult weighing 70 kg, ibuprofen at 10 mg/kg (educational example). Total dose = 700 mg. Nearest available tablet: 400 mg (commonly rounded down or to nearest available strength).

Understanding Your Results

The calculated dose is a starting point based on published mg/kg guidelines. Actual prescribed doses may differ based on renal function, hepatic function, drug interactions, indication, and patient-specific factors only a prescriber can fully assess.

Common Mistakes to Avoid

• Using body weight for obese patients without adjusting to ideal or adjusted body weight for weight-sensitive drugs.
• Ignoring maximum dose limits — many drugs have absolute daily maximums that override weight-based calculations.
• Confusing mg/kg/day with mg/kg/dose — the frequency of dosing is critically important.
• Administering a calculated dose without verifying it against the prescriber's written order.