👶 Infant Tylenol Dosage Calculator

Infant acetaminophen (Tylenol) is dosed by weight, not age: 10 to 15 mg per kilogram of body weight per dose, every 4 to 6 hours as needed, with no more than 5 doses in 24 hours. This calculator converts pounds to kilograms, computes the milligram range, and translates it into milliliters of standard 160 mg per 5 mL infant liquid.

Treat this as a double-check, not a prescription. Dosing errors in infants usually come from confusing teaspoons with milliliters or from stacking acetaminophen hidden in combination cold products. Always confirm the dose with your pediatrician or pharmacist, especially for a baby under 12 weeks old.

How to Use This Calculator

Weigh the baby in pounds, or convert from kilograms by multiplying by 2.2. Select the age band: under 12 weeks gets a call-the-doctor message instead of a routine dose. Read the milliliter range per dose, the dosing interval, and the 24-hour maximum. Measure with the oral syringe that comes with the medicine, never a kitchen spoon.

The Weight-Based Dosing Rule

The 10 to 15 mg per kg range comes from pediatric references including the Harriet Lane Handbook and FDA labeling for infant acetaminophen. The range exists because fever control is the goal, not a magic number: 10 mg/kg often suffices, and 15 is the per-dose ceiling. The 24-hour ceiling of 75 mg/kg (5 doses) protects the liver, since acetaminophen overdose injures the liver silently before symptoms appear. Concentration matters enormously: US infant liquid is standardized at 160 mg per 5 mL, and using the wrong concentration in the math is the classic error this calculator is designed to prevent.

Worked Example

An 18-pound baby weighs about 8.2 kg (18 lb). At 10 to 15 mg per kg, one dose is 82-122 mg per dose, which is 2.6 to 3.8 mL of standard 160 mg/5 mL liquid. The daily ceiling is 612 mg (5 doses max), meaning no more than five doses in 24 hours even if the fever returns sooner. Under 12 weeks, the answer is different: Standard 10-15 mg/kg dosing applies.

Reading the Result Safely

The result is a range, not a single number, because both ends of the 10 to 15 mg/kg band are acceptable. Start at the lower end if the fever is mild. The "every 4 to 6 hours" interval means you may give the next dose no sooner than 4 hours later, and the 5-dose daily cap overrides everything: even if doses were given at minimum intervals, stop at five. Check every other medicine the baby takes for hidden acetaminophen (often listed as APAP), since combination products are the most common cause of accidental double-dosing.

Call the Doctor Instead of Calculating

Call your pediatrician before any dose for a baby under 12 weeks with a fever of 100.4 F (38 C) or higher: that is an automatic evaluation, not a Tylenol situation. Also call for any baby with trouble breathing, unusual sleepiness, dehydration, a rash with fever, or fever lasting more than 3 days. Never give ibuprofen to a baby under 6 months. This tool is for informational purposes only, not medical advice. Dosing decisions must be confirmed with your doctor or pharmacist. Consult a healthcare professional.

Related tools: ibuprofen-style weight dosing basics and when fever needs care.

For informational purposes only, not medical advice. Dosing decisions must be confirmed with your doctor or pharmacist. Consult a healthcare professional.