Weight-Based Dosage Calculator

Scale mg/kg/day or mg/kg/dose orders to total daily and per-dose amounts from patient weight.

Written by

Sid A. Abdala Balal

RGN · Medical & Nursing Content Author

Medically reviewed by

Dr. Adam Sayedi

MD · Emergency & Acute Medicine

⚠️ Safety note: High-risk: verify pediatric and weight-based orders with pharmacy and your unit protocol — never rely on a calculator alone.

Understanding this tool

Why nurses use it

Many paediatric and adult protocols scale medication to body weight (mg/kg or mcg/kg). Ward nurses use weight-based math to verify pharmacy labels, prepare split doses, or double-check calculations during medicines administration.

When to use it

Use when an order specifies mg/kg/day or mg/kg/dose and you know the patient’s weight. Select the dose basis to match the prescription. Confirm whether the order uses actual weight, ideal body weight, or adjusted body weight per protocol.

Calculate

How to use this calculator

Obtain current weight in kg (or convert using the unit selector).
Select dose basis: mg/kg/day or mg/kg/dose.
Enter the ordered dose per kg and doses per day.
Compare the result with the pharmacy label and maximum dose limits.

How the calculation works

mg/kg/day: total daily dose = dose × weight; per dose = total ÷ frequency. mg/kg/dose: per dose = dose × weight; total daily = per dose × frequency. Always check drug-specific maximum doses.

mg/kg/day: total = dose × weight; per dose = total ÷ frequency. mg/kg/dose: per dose = dose × weight; total = per dose × frequency.

Formula used by this tool — verify units before applying at the bedside.

Worked example

70 kg × 10 mg/kg/day BID → 700 mg/day, 350 mg per dose.

Limitations & clinical notes

Check maximum single and daily doses for the specific drug.
Use actual body weight or protocol-specified weight (IBW/AdjBW) as ordered.
Select mg/kg/day or mg/kg/dose to match the prescription wording.

References

Key sources: BNF — Prescribing in children.

Disclaimer: This calculator is for educational and bedside double-check purposes only. It does not replace institutional protocols, prescriber orders, pharmacist verification, or clinical judgment. Always follow your local policies — especially for high-risk medications, infusions, pediatrics, and critical care. If the patient is acutely unwell, escalate immediately rather than relying on any calculator output.