Calculate infant and children's acetaminophen (Tylenol) dosage by weight with multiple formulations, dosing chart, and toxicity thresholds.
Acetaminophen (Tylenol, paracetamol) is the most commonly used medication for fever and pain relief in infants and children, and it is the only analgesic/antipyretic recommended for infants under 6 months of age (ibuprofen is not approved until 6 months). The standard pediatric dose is 10–15 mg/kg per dose, given every 4–6 hours as needed, with a maximum of 5 doses in 24 hours (75 mg/kg/day or 4,000 mg/day, whichever is lower).
This infant and children's Tylenol dosage calculator determines the precise dose based on the child's weight, converts it to the specific formulation being used (infant drops, children's liquid, chewable tablets, junior tablets, or rectal suppositories), and checks against maximum dose limits and toxicity thresholds. The calculator addresses one of the most common sources of pediatric medication errors: the multiple commercially available concentrations of acetaminophen that can be easily confused. Since 2011, infant drops and children's liquid now share the same concentration (160 mg/5 mL) in the US, but older stock of the concentrated infant drops (80 mg/0.8 mL) may still exist in some households.
Acetaminophen is generally safe at therapeutic doses but has a narrow margin between therapeutic and toxic doses compared to ibuprofen. Accidental overdose is a leading cause of acute liver failure in children, making accurate weight-based dosing essential. This calculator includes age/weight presets, formulation-specific volume calculations, and a clear toxicity threshold reference table to support safe use.
Acetaminophen has a narrower therapeutic-to-toxic ratio than many parents realize, and the multiple available formulations with different concentrations create a significant potential for dosing confusion. This calculator ensures accurate weight-based dosing, converts to the exact formulation volume, flags doses approaching toxic thresholds, and provides a reference chart matching the format parents encounter on OTC packaging — reducing the most common pediatric medication errors.
Single dose = weight (kg) × 10–15 mg/kg (maximum 1,000 mg). Volume (liquid) = dose (mg) ÷ concentration (mg/mL). Maximum daily dose = 75 mg/kg/day or 4,000 mg, whichever is lower. Dosing interval: every 4–6 hours, no more than 5 doses in 24 hours.
Result: 150 mg (4.7 mL) every 6 hours
A 10 kg infant: 10 × 15 = 150 mg per dose. Using 160 mg/5 mL drops: 150 ÷ 32 = 4.7 mL per dose. Four doses per day (every 6 hours): 600 mg/day total = 60 mg/kg/day, within the 75 mg/kg/day limit.
Acetaminophen (paracetamol) works primarily through central inhibition of cyclooxygenase pathways and activation of descending serotonergic inhibitory pathways, producing analgesia and antipyresis without significant anti-inflammatory effect. In children, it is absorbed rapidly from the GI tract with peak plasma levels at 30–60 minutes. The half-life is approximately 2–4 hours. Metabolism occurs primarily via hepatic glucuronidation and sulfation (which predominates in young children), with a small fraction metabolized by CYP2E1 to the toxic metabolite NAPQI, which is normally neutralized by glutathione.
Prior to 2011, infant acetaminophen drops were sold at a concentrated 80 mg/0.8 mL (100 mg/mL) to allow small-volume dosing with droppers. Children's liquid was 160 mg/5 mL (32 mg/mL) — more than three times less concentrated. This concentration mismatch caused numerous dosing errors when caregivers used the children's liquid measuring cup with infant drops or vice versa. In 2011, the FDA and manufacturers unified the concentration to 160 mg/5 mL for both products, but the old concentrated drops may still be found in some medicine cabinets, making label verification essential.
Acetaminophen toxicity occurs above approximately 150 mg/kg in a single dose or 75 mg/kg/day for multiple-day dosing. Toxicity produces NAPQI accumulation that depletes hepatic glutathione and causes centrilobular hepatic necrosis. N-acetylcysteine (NAC) is the specific antidote and is most effective when administered within 8 hours of overdose ingestion. Parents should keep the Poison Control number (1-800-222-1222 in the US) accessible and seek immediate medical attention for any suspected overdose, even if the child appears well initially.
The standard dose is 10–15 mg/kg per dose based on the infant's weight, given every 4–6 hours as needed. Always use a calibrated syringe and the specific formulation's dosing chart. For infants under 3 months, consult your pediatrician before giving any acetaminophen.
In the US since 2011, yes — both are 160 mg/5 mL. However, old stock of the concentrated infant drops (80 mg/0.8 mL, now discontinued) may still exist. Always check the label concentration before dosing. In some countries, concentrations may differ.
Early symptoms (first 24 hours) include nausea, vomiting, and abdominal pain. Liver damage may not be apparent until 24–72 hours. Any suspected overdose (≥ 150 mg/kg single dose) requires immediate emergency evaluation and potential N-acetylcysteine (NAC) treatment.
Yes, acetaminophen and ibuprofen can be alternated for persistent fever. They work by different mechanisms and have independent dose limits. A common schedule is acetaminophen, then ibuprofen 3 hours later, alternating every 3 hours. Ibuprofen cannot be used until 6 months of age.
For fever, no more than 3 days without consulting a doctor. For pain, no more than 5 days. If fever persists beyond 3 days or pain beyond 5 days, the child should be evaluated by a healthcare provider to determine the underlying cause.
If the child vomits within 15–20 minutes of taking the dose, you can repeat the full dose once. If they vomit after 20 minutes, the medication was likely partially absorbed — do not repeat. Wait until the next scheduled dose time. Rectal suppositories are an alternative for vomiting children.