Dosage Calculator
Work out a weight-based dose in mg/kg, the total daily amount, and the liquid volume to measure for a given concentration, with checks against the maximum single and daily dose you enter from the label or prescription. Example: 20 kg at 15 mg/kg every 6 hours is 300 mg per dose, 1,200 mg a day, or 9.4 mL of a 160 mg per 5 mL liquid.
Show steps
How to use the Dosage Calculator
- Enter the weight and the mg/kg dose that your prescriber or the label gives.
- Enter the number of doses per day, and the liquid strength if you are measuring a liquid.
- Enter the label maximums to get a warning if the result goes over them, then press Calculate.
Formula and method
Dose (mg) = weight (kg) x dose (mg/kg). Daily total = dose x number of doses. Volume (mL) = dose (mg) / concentration (mg/mL), where concentration = mg of drug / mL of liquid. Pounds to kilograms: divide by 2.2046.
Worked example
| Step | Result |
|---|---|
| Weight | 20 kg |
| Dose 15 mg/kg | 300 mg |
| 4 doses a day | 1,200 mg |
| Liquid 160 mg per 5 mL = 32 mg/mL | 9.4 mL per dose |
Safety checklist
| Check | Why |
|---|---|
| Confirm the mg/kg dose with a pharmacist or prescriber | Doses differ by drug, age and condition |
| Check the liquid strength on the bottle | Different products have different mg per mL |
| Use a marked oral syringe | Household spoons vary widely |
| Respect the maximum single and daily dose | Prevents overdose |
| Write down the time of each dose | Avoids double dosing |
Pounds to kilograms
Divide pounds by 2.2046. For example 44 lb is 20 kg. Always use the current weight, not an old one.
When not to use this
Do not use it for insulin, heparin, chemotherapy, opioids in infants or any high-alert medicine, or in emergencies. Call your local poison control center or emergency number if a possible overdose has happened.
Frequently asked questions
How do I calculate a dose from weight?
Multiply the weight in kilograms by the dose in mg per kg.
How do I convert mg to mL?
Divide the dose in mg by the concentration in mg per mL.
Can I use this for my child?
Only to double-check math from your pediatrician or the label, never to choose a dose.
What if the calculated dose is above the maximum?
Use no more than the maximum and ask the prescriber.
Why use a syringe instead of a spoon?
Spoons can be off by 50 percent or more.
What do I do after a suspected overdose?
Call poison control or emergency services right away.
Sources
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