Child Medicine Dosage Calculator

Child medication dosing by weight uses the child’s weight (not age) to calculate the correct dose of common over-the-counter medicines. Weight-based dosing is more accurate because children of the same age can vary significantly in body mass.

Core dosing formula: Dose (mg) = Child Weight (kg) × Dose per kg (mg/kg) Volume to give (mL) = Dose (mg) ÷ Concentration (mg/mL)

What each variable means:

• Child Weight — always measure in kilograms for medical dosing. To convert: Weight (kg) = Weight (lbs) ÷ 2.205.
• Dose per kg (mg/kg) — the recommended therapeutic dose per kilogram of body weight. This comes from clinical studies that established effective and safe amounts.
• Concentration (mg/mL) — the strength of the liquid medicine. Always check the bottle — concentrations vary between brands and formulations.
• Volume — the actual amount of liquid (mL) you measure and give. Use the measuring syringe included with the medicine, not a household teaspoon.

Acetaminophen (Children’s Tylenol) dosing: Dose = 15 mg/kg per dose, every 4–6 hours, max 5 doses/day Standard infant concentration: 160 mg/5 mL

Ibuprofen (Children’s Advil) dosing: Dose = 10 mg/kg per dose, every 6–8 hours (only for children 6+ months) Standard concentration: 100 mg/5 mL

Worked example: Child weighs 18 kg (approximately 40 lbs). Needs acetaminophen.

Dose = 18 kg × 15 mg/kg = 270 mg Concentration = 160 mg/5 mL Volume = 270 ÷ 160 × 5 = 8.4 mL

For ibuprofen: Dose = 18 kg × 10 mg/kg = 180 mg Volume = 180 ÷ 100 × 5 = 9.0 mL

Maximum dose caps:

• Acetaminophen: never exceed 1,000 mg per dose or 4,000 mg/day (adult limits)
• Ibuprofen: never exceed 400 mg per dose for children
• Children under 2: always check with a physician before giving any OTC medication

Safety reminders: Never give aspirin to children (Reye’s syndrome risk). Never give ibuprofen to infants under 6 months. Use only the measuring device provided in the package — kitchen spoons are inaccurate.