Medication Dosage Calculator
Enter the weight and the dose written on a prescription or label to convert it into milligrams, millilitres or tablets, with warnings if a maximum you enter is passed.
This tool does the arithmetic only. It does not know any medicine and never suggests a dose. Enter the dose and limits exactly as written on your prescription or the product label, and check the answer with a pharmacist or doctor. For infants and young children a small error can cause harm. In an emergency or a suspected overdose, call your local emergency number or poison control straight away.
What this calculator does
Some prescriptions give a dose in milligrams per kilogram of body weight. To use one you multiply the weight by the dose, work out how much liquid or how many tablets that makes, and check the total against the daily maximum. This tool does those multiplications and divisions for you, and nothing more.
You supply every medical figure. The dose per kg, the doses per day, the strength of the liquid or tablet and any maximums all come from the prescription, the product label or your pharmacist. The page has no medicine list and will not suggest or confirm a dose. It also cannot know whether a medicine suits the person taking it.
How it's worked out
The dose in milligrams is the weight in kilograms times the dose per kg. If you enter a maximum single dose and the weight-based dose is higher, the maximum is shown instead and you are warned. The daily total is that dose times the number of doses per day, and you are warned if it passes the daily maximum you entered. Liquid volume is the dose divided by the strength in mg per mL, and tablets are the dose divided by the tablet strength.
Arithmetic example
The numbers below only show how the calculation works and are not a recommended dose for any medicine. A child weighing 20 kg with a written dose of 10 mg per kg, given 3 times a day, comes to 200 mg per dose and 600 mg in 24 hours. With a liquid of 40 mg per mL, 200 mg is 5 mL.
Staying safe
Always use the measuring device that comes with the medicine, such as an oral syringe, and never a kitchen spoon. Do not combine medicines that contain the same ingredient. If the result looks high, or does not match the label, stop and ask a pharmacist or doctor. For other health numbers you can use the BMI Calculator or the Unit Converter for weight conversions.
Frequently asked
Does this calculator tell me how much of a medicine to give?
No. It does arithmetic using the dose you enter from a prescription or label. It has no medicine information and never recommends a dose.
Where do I find the dose per kg?
It is written on the prescription or comes from your doctor or pharmacist. Never guess it or take it from a web page. If the label gives a dose by age or weight range instead, follow the label.
How do I enter a liquid strength given as mg per 5 mL?
Divide the milligrams by 5. For example 200 mg per 5 mL is 40 mg per mL.
Why do maximums matter?
A weight-based dose can come out higher than the safe single dose or daily limit, especially for heavier people. If you enter the maximums from the label, the calculator shows the lower figure and warns you when a limit is passed.
Is this suitable for babies or children?
Dosing for infants and children needs extra care, because small errors matter. Use the prescription or the product label as the source, check any result with a pharmacist, and do not rely on this page alone.