How the dosage calculator works
Many medicines, especially for children, are dosed by body weight in milligrams per kilogram. The calculation has two steps: convert weight to kilograms and multiply by the ordered mg/kg, then convert the dose in milligrams to a liquid volume using the concentration on the bottle.
Dose (mg) = Weight (kg) × mg/kg
Volume (mL) = Dose (mg) ÷ (concentration mg ÷ 5 mL)
Concentration is entered per 5 mL, the way most US oral liquids are labelled (for example 160 mg/5 mL). If your product lists mg per mL, multiply it by 5 before entering. If you enter a maximum single dose, the result is capped there. Nurses and pharmacists use this "dimensional analysis" check routinely to catch errors.
Worked example
A child weighs 44 lb (19.96 kg) and the order is 15 mg/kg of acetaminophen. The dose is 19.96 × 15 = 299.4 mg. At 160 mg per 5 mL (32 mg/mL) the volume is 299.4 ÷ 32 = 9.36 mL. A label maximum single dose of 15 mg/kg up to 1,000 mg would not limit this dose.
For education only. Not medical advice; confirm with a qualified clinician.
Frequently asked questions
How do I convert pounds to kilograms for dosing?
Divide pounds by 2.2046, or multiply by 0.4536. 44 lb is about 20 kg.
What does mg/kg mean?
Milligrams of drug per kilogram of body weight. A 20 kg child at 10 mg/kg gets 200 mg.
Can I use this to decide a dose for my child?
No. Use it only to check the arithmetic of a dose from a clinician or label. Dose choices depend on age, health and other medicines.
Why is there a maximum dose?
Weight-based doses can exceed adult maximums for heavier patients, so labels set an upper limit per dose and per day.
Updated October 2026. Results are estimates for education, not financial or medical advice. All math runs in your browser; nothing you type is sent anywhere.