Weight-based children's acetaminophen & ibuprofen doses — the label math, done carefully
| Weight | Acetaminophen 160mg/5mL | Ibuprofen 100mg/5mL |
|---|
Children's medication dosing is weight-based math that the box turns into age brackets — and age brackets are why dosing errors are so common: a heavy 2-year-old and a light 4-year-old need very different amounts than their "age" suggests. This reference does the weight-based calculation (the method pediatricians use) for the two standard children's liquids — acetaminophen 160mg/5mL and ibuprofen 100mg/5mL — with the intervals, daily maximums and hard red lines stated plainly.
| Acetaminophen (Tylenol) | Ibuprofen (Motrin/Advil) | |
|---|---|---|
| Dose | 10–15 mg/kg | 5–10 mg/kg |
| Interval / max | Every 4–6h, max 5 doses/24h | Every 6–8h, max 4 doses/24h |
| Age floor | 12+ weeks OTC (younger = doctor first, always) | 6+ months, firm |
| Notes | Gentler on stomach; the overdose-risk one — count every source | Anti-inflammatory too; give with food; avoid in dehydration/vomiting |
Fever is immune function, not the enemy — treat the child's comfort, not the number. See a doctor now for: any fever under 3 months old (this is an ER/urgent rule, not a suggestion), fever above 104°F unresponsive to meds, stiff neck, unusual drowsiness, dehydration, difficulty breathing, rash with fever, or fever beyond 2–3 days. And never aspirin for children (Reye's syndrome).
Weight determines drug distribution; age merely correlates with weight. The box uses age for simplicity, which misdoses kids at the ends of the weight curve. Pediatricians dose mg/kg — this reference shows that math.
They can be alternated for stubborn fevers (different mechanisms, different clearance) but only on a written schedule, ideally pediatrician-blessed — free-styling two clocks is how interval errors happen. Never double up doses of the SAME ingredient across products.
Within ~15 minutes and you can see it came up: generally repeat once. Later than that, assume absorption and wait for the next interval. Repeated vomiting is itself a call-the-doctor sign (and a reason to avoid ibuprofen).
Once weight-based dose ≈ adult dosing (~around 95-100 lb for many products), children can take adult formulations — but check with the pharmacist for the specific product; chewables and junior strengths bridge the gap safely.
Under 12 weeks (acetaminophen) or 6 months (ibuprofen): doctor first, no exceptions — partly because fever that young is itself the emergency to evaluate, not the symptom to mask.
No — it's the weight-based math with safety context, for education and label-checking. The label on YOUR bottle and your pediatrician's advice govern; when they disagree with any calculator, they win.
Yes — weights and selections never leave your browser.
Weigh the child, use the syringe, log the time, count every acetaminophen source — four habits that eliminate nearly all home dosing errors. And keep the pediatrician's number where the thermometer lives.