Drug Dosage Calculator

Enter your patient weight, prescribed dosage, dose frequency, and liquid formulation details to calculate the exact volume per dose your patient needs. The Drug Dosage Calculator helps clinicians and caregivers determine how many milliliters of a liquid medication to administer based on weight-based dosing protocols.

Disclaimer: This tool is for informational and educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before making any health-related decisions.

kg

Enter the patient's body weight in kilograms.

mg/kg/day

The prescribed dose in mg per kg of body weight per day.

How many times per day the medication is administered.

mg

The amount of active drug in the liquid formulation (e.g. 250 mg).

mL

The volume of liquid that contains the medication amount above (e.g. 5 mL).

Results

Volume Per Dose

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Dose Per Administration

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Total Daily Dose

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Total Daily Volume

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Results Table

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Frequently Asked Questions

How is a weight-based drug dose calculated?

A weight-based dose is calculated by multiplying the patient's body weight (in kg) by the prescribed dose per kg per day (mg/kg/day). This gives the total daily dose in mg. That total is then divided by the number of administrations per day to get the dose per administration.

How do I convert the dose in mg to a liquid volume in mL?

Once you know the dose per administration in mg, divide it by the drug concentration of your liquid formulation. For example, if the formulation is 250 mg per 5 mL, the concentration is 50 mg/mL. Dividing the dose in mg by 50 mg/mL gives you the volume in mL to administer.

What does frequency of dose mean?

Frequency refers to how many times per day the medication is given. Common frequencies include once daily (QD), twice daily (BID), three times daily (TID), and four times daily (QID). The total daily dose is split equally across each administration.

Can I use this calculator for pediatric patients?

Yes. Weight-based dosing is especially common in pediatric medicine. Simply enter the child's weight — either in kg or lbs — along with the prescribed mg/kg/day dosage and formulation details. Always confirm pediatric dosing with a licensed prescriber or pharmacist.

What if my patient's weight is in pounds instead of kilograms?

Select 'Pounds (lbs)' in the weight unit dropdown. The calculator will automatically convert the weight to kilograms (by dividing by 2.2046) before performing the dose calculation.

Is this calculator a substitute for professional medical advice?

No. This tool is intended for educational and reference purposes only. All medication dosing decisions should be verified by a licensed healthcare professional, pharmacist, or prescriber before administration. Drug dosing can be affected by factors such as renal function, age, and drug interactions that this calculator does not account for.

What is the liquid formulation concentration?

The liquid formulation concentration is expressed as the amount of active drug (in mg) contained in a given volume of liquid (in mL). For example, amoxicillin suspension is often available as 250 mg per 5 mL. Entering these two values allows the calculator to determine exactly how many mL to give per dose.

Why do different frequencies result in different volumes per dose?

The total daily dose stays constant based on the patient's weight and prescribed mg/kg/day. When you increase the frequency (e.g. from once daily to three times daily), each individual dose is smaller, so the volume per administration decreases accordingly — while the total daily volume remains the same.