How this instrument works
This tool takes a child's weight in kilograms and applies the standard pediatric ibuprofen range of 5 to 10 mg per kilogram per dose, repeated every 6 to 8 hours, with no more than four doses in 24 hours. Treat the output as an educational reference for the arithmetic, never as medical advice: confirm any dose with your child's pediatrician or a pharmacist first, measure only with the syringe or cup that came in the box — a kitchen spoon is not accurate enough — and if you suspect an overdose or are unsure what was already given, call Poison Control at 1-800-222-1222 (US) or emergency services immediately.
Ibuprofen carries two cautions that acetaminophen mostly avoids. It is not recommended for infants younger than six months old — a safe dose has not been established for that age group, and this calculator should not be used there without a doctor's specific direction. It also affects the kidneys in a way acetaminophen does not: a child who is dehydrated, whether from vomiting, diarrhea, or simply poor fluid intake during a fever, faces a higher risk of a kidney-related reaction to an NSAID like ibuprofen. When fluids are down and a fever still needs treating, that combination is worth a call to the pediatrician before reaching for this medication, not after.
The 24-hour ceiling shown here is a flat 40 mg per kilogram per day, tracked separately from the per-dose range. It rises with weight the same way the per-dose figures do, since both scale off the same number, but it is not simply four times the high-end dose — check it on its own each time, especially on a day when a fever has doses running closer together than the label's every-6-to-8-hour spacing.
- Enter the child's weight in kilograms — divide pounds by 2.2 first if that's what you have.
- Read the per-dose range in milligrams, then the same range converted to mL of 100 mg/5 mL suspension.
- Check the 24-hour maximum in mg before giving a second, third, or fourth dose.
- Confirm the figure with a pediatrician or pharmacist, and measure only with the dosing syringe supplied with the product.
Worked example — 20 kg child
A 20 kg child: low end is 5 × 20 = 100 mg, high end is 10 × 20 = 200 mg per dose. At the standard 100 mg/5 mL suspension, that's 100 ÷ 100 × 5 = 5.00 mL on the low end and 200 ÷ 100 × 5 = 10.00 mL on the high end — a full dosing cup's worth of range depending on how the fever is running.
The 24-hour maximum for this child is 40 × 20 = 800 mg, roughly four doses at the high end spread across the day. A lighter 10 kg child scales down the same way: 5 × 10 = 50 mg to 10 × 10 = 100 mg per dose, 2.50-5.00 mL, with a daily ceiling of just 40 × 10 = 400 mg — a reminder that smaller children reach their limit on far fewer doses than a bigger sibling would.
Questions
Is this calculator a substitute for asking a doctor or pharmacist?
No. Treat every figure here as a starting point to confirm, never as a final answer. Call your child's pediatrician or pharmacist before the first dose of a new medication, whenever weight changes significantly, and whenever dehydration, kidney disease, or asthma might change the safe range. If you suspect an overdose or gave a dose you're unsure about, contact Poison Control at 1-800-222-1222 (US) immediately, or call emergency services — do not wait to see whether symptoms show up first.
Why shouldn't ibuprofen be given to infants under 6 months old?
Because a safe dose has not been established for that age group, and young infant kidneys handle the drug differently than an older child's do. The FDA-reviewed labeling for children's ibuprofen restricts routine use to 6 months and older; below that, acetaminophen is the usual fallback, and any exception needs a pediatrician's specific direction rather than this calculator's arithmetic.
Why does dehydration matter specifically for ibuprofen?
Because ibuprofen, like other NSAIDs, partly relies on kidney blood flow that gets tighter when a child is already short on fluids from vomiting, diarrhea, or poor intake during illness. Combining dehydration with an NSAID raises the risk of a kidney-related reaction that acetaminophen, which does not work the same way, mostly avoids. A pediatrician may prefer acetaminophen or IV fluids first in that situation rather than ibuprofen.
How is ibuprofen dosing different from acetaminophen dosing?
The per-kilogram range is different (5-10 mg/kg versus 10-15 mg/kg), the standard liquid concentration is different (100 mg/5 mL versus 160 mg/5 mL), the frequency is different (every 6-8 hours versus 4-6), and the maximum doses per day is different (four versus five). Never assume the two medications share a chart — mixing up the numbers is exactly the kind of error a caregiver should double-check against the actual product label.
What if a dose is given a little late?
Give it when you remember and resume the normal 6-8 hour spacing from that point — do not give a double dose to make up for lost time, and do not compress the interval to catch up. If more than one dose was accidentally given close together, that's a reason to call Poison Control at 1-800-222-1222 (US) rather than guess.
Can I measure a dose with a kitchen spoon instead of the syringe?
No — never a household spoon. Kitchen teaspoons vary widely in actual volume, and caregiver dosing-error studies consistently find spoon-measured doses running outside the intended range. Use only the oral syringe or dosing cup that came with the product; a pharmacist can supply a replacement free of charge if it's been lost.
References
- DailyMed — Children's Motrin (ibuprofen) Oral Suspension, FDA Drug Facts Label
- HealthyChildren.org (American Academy of Pediatrics) — Ibuprofen Dosing Table for Fever and Pain
Read this first: This instrument computes a screening figure from population formulas — it is not a diagnosis, and it cannot see the whole picture a clinician can. Use it to inform a conversation, not to replace one.