Nursing Dosage Calculator
This dosage calculator uses the desired-over-have method to convert an ordered dose into the volume (mL) or number of tablets to administer, with an optional weight-based (mg/kg) mode and the worked dimensional-analysis steps.
Calculator
LiveEducational tool, not medical advice. Verify every dose against the prescription and your institutional protocol — a licensed clinician is responsible for the final dose.
Enter values to see your result.
How to Use the Calculator
- Choose liquid (mL) or tablet form.
- Enter the ordered (desired) dose, or switch on weight-based mode and enter weight + mg/kg.
- Enter the available stock strength, and for liquids the stock volume.
- Read the amount to administer and the worked steps.
What the Result Means
The result is the volume (mL) or number of tablets that delivers the ordered dose. If it exceeds two tablets or a large volume, the calculator flags it so you can double-check the order, the available strength, and the route before administering.
When to Use This Calculator
- Bedside medication administration (mL or tablets)
- Nursing school and NCLEX dosage practice
- Weight-based (mg/kg) dose checks
Frequently Asked Questions
What is the desired-over-have formula?
Volume to give = (Desired dose ÷ Dose you have on hand) × Quantity (the volume that contains the "have" amount). For tablets, simply divide the desired dose by the strength per tablet.
How do I calculate the mL to administer?
Divide the ordered dose by the available stock strength, then multiply by the stock volume. For example, 500 mg ordered, 250 mg/5 mL on hand: (500 ÷ 250) × 5 = 10 mL.
How does weight-based (mg/kg) dosing work?
Multiply the patient weight in kilograms by the prescribed mg/kg to get the ordered dose, then apply the desired-over-have method to find the volume or tablets to give.
References & Guidelines
- ISMP. Safe practices for medication dosing and administration.
- Standard nursing pharmacology and dosage-calculation references.