Weight-Based Dosage Calculator
What is Weight-Based Dosage Calculator
A weight-based dosage calculator works out the total dose of a medication from the patient's weight and a per-kilogram dose (mg/kg). It multiplies weight by the dose, caps the result at an optional maximum, and, if you give the liquid concentration (mg/mL), returns the volume to draw up. The core formula is total dose (mg) = weight (kg) times dose (mg/kg).
How to use
- Enter the patient's weight in kilograms.
- Enter the dose per kilogram in mg/kg.
- Optionally enter a maximum dose in mg to cap the result.
- Optionally enter the concentration in mg/mL to get the volume to give.
When to use it
Dosing a 20 kg child with an antibiotic at 25 mg/kg? Enter both and you get a 500 mg dose, and with a 50 mg/mL suspension that is 10 mL to draw up. Add a maximum dose and the tool flags when the weight-based amount would exceed the adult ceiling.
Frequently asked questions
What is the formula for a weight-based dose?
Total dose (mg) = weight (kg) × dose (mg/kg). For a 20 kg child at 25 mg/kg, that is 20 × 25 = 500 mg. If a maximum dose is set and the result is higher, the dose is capped at that maximum.
What is the maximum dose for?
Many drugs have an adult ceiling, for example 10 mg/kg up to a maximum of 500 mg. Once a heavier patient's weight-based amount passes that ceiling, the dose stops increasing. Enter it and the tool caps the result and flags it.
How do I get the volume in mL?
Volume (mL) = dose (mg) ÷ concentration (mg/mL). For a 500 mg dose with a 50 mg/mL suspension, that is 500 ÷ 50 = 10 mL. Leave the concentration blank if you only need the dose in mg.
Can I share this tool with my inputs pre-filled?
Yes. The URL updates automatically as you type. Copy it from the address bar or use the Share button — anyone who opens the link will see your exact inputs ready to go.
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