Ibuprofen — sold as Advil, Motrin, Nurofen, and generic store brands — is one of the most common over-the-counter fever and pain medicines on the market. The trouble is that the bottle label only gives a rough age-based table, while the truly safe dose depends almost entirely on body weight. Giving too little leaves a fever untreated; giving too much raises the risk of stomach, kidney, and bleeding side effects. This ibuprofen dosage calculator converts body weight into a precise milligram dose and then into the exact milliliters of liquid suspension (or the number of tablets) to give, using the standard weight-based regimen trusted by pediatric hospitals.
Adjust the inputs and every figure updates instantly. You can switch between the mild 5 mg/kg dose and the full 10 mg/kg dose, and the tool will also show the 24-hour maximum so you never accidentally over-medicate.
How to Use
- Enter the person's Body Weight in kilograms (or convert pounds by dividing by 2.2). Weight-based dosing is far more accurate than guessing by age, especially for children who are smaller or larger than average.
- Set the Dose per kg. Use 5 mg/kg for mild fever or minor aches, and 10 mg/kg when the fever is high or the pain is stronger. The children's range is 5–10 mg/kg per dose.
- Check the Liquid Strength on the bottle. Standard children's oral suspension is 100 mg per 5 mL (that is 20 mg per mL). Infant drops and concentrated suspensions may differ, so read the label carefully rather than assuming.
- Choose how often you plan to repeat the dose under Repeat Every — 6 or 8 hours. Ibuprofen should never be given more often than every 6 hours.
- Read the result card: the milligrams and milliliters per single dose, the safe 24-hour ceiling, and the maximum number of doses you may give in a day.
If the person takes adult tablets instead of liquid, the calculated milligram dose tells you how many 200 mg tablets to round toward — adults typically take 200–400 mg per dose, while children should almost always use the weight-based figure.
The Dosing Formula
The standard children's ibuprofen regimen is weight-based:
Single dose (mg) = body weight (kg) × dose (5–10 mg/kg)
The suspension converts milligrams into liquid volume. Because 100 mg of children's suspension fills 5 mL, each milliliter holds 20 mg:
Liquid dose (mL) = dose (mg) ÷ 20 (mg/mL)
The safety ceiling is 40 mg per kilogram of body weight over 24 hours. At 10 mg/kg per dose that means no more than about 4 doses in a day; at 5 mg/kg you may reach the ceiling sooner by volume, so always count the doses. For reference, the recommended adult OTC dose is 200–400 mg every 4–6 hours, and the adult daily ceiling is 1,200 mg unless a doctor directs otherwise.
Worked example for a 30 kg child on the full 10 mg/kg dose: 30 × 10 = 300 mg per dose, and 300 ÷ 20 = 15 mL of suspension. The 24-hour maximum is 30 × 40 = 1,200 mg, which equals 60 mL — so four 15 mL doses fill the day exactly.
Liquid, Tablets, and Topical Forms
Children usually take ibuprofen as an oral suspension (100 mg/5 mL). The measuring cup or syringe that comes in the box is calibrated to that 20 mg/mL strength — a "teaspoon" on an old label means 5 mL. Adults more often use 200 mg film-coated tablets, or 400 mg and 600 mg strengths from a pharmacy. There are also 5% ibuprofen topical gels applied to sore joints, but those are absorbed through the skin and are not part of the oral dose this calculator works out. A bottle of children's suspension typically costs about $8–$12, and a single tube of 5% gel runs around $10–$15.
Never combine two different ibuprofen products at once, and keep infant drops (which used to be a stronger concentration) separate from the standard 100 mg/5 mL children's suspension unless you have checked each label.
Examples
Example 1 — A 30 kg child with a fever. Enter 30 kg, 10 mg/kg, and the standard 100 mg/5 mL strength. The result is 300 mg (15 mL) per dose, repeat every 6–8 hours, with a 24-hour ceiling of 1,200 mg (60 mL) — about 4 doses maximum.
Example 2 — A smaller 15 kg child, mild discomfort. On the gentle 5 mg/kg setting: 15 × 5 = 75 mg, which is 75 ÷ 20 = 3.75 mL per dose. The daily ceiling is 600 mg (30 mL), and at this lower per-dose strength you could give up to 8 doses by weight, though you would still spread them at least 6 hours apart.
Example 3 — Stress test on a large body. Because the dose scales linearly with weight, an adult weighing, say, 70 kg on 10 mg/kg would compute to 700 mg — but that exceeds the adult OTC single-dose limit of 400 mg, which is exactly why adults should use the labeled 200–400 mg tablets rather than the pediatric weight formula.
FAQ
How much ibuprofen can I give per kilogram?
The standard children's dose is 5–10 mg per kilogram of body weight per dose, repeated every 6–8 hours. Use 5 mg/kg for mild symptoms and 10 mg/kg for higher fever or stronger pain. The safe 24-hour maximum is 40 mg/kg total, divided across the day's doses.
How do I convert milligrams of children's ibuprofen into mL?
Standard children's ibuprofen suspension is 100 mg per 5 mL, which equals 20 mg per mL. Divide the milligram dose by 20 to get milliliters. For example, a 100 mg dose is 5 mL, and a 300 mg dose is 15 mL. Always use the syringe or cup from the actual bottle, since other concentrations exist.
What is the maximum ibuprofen dose per day?
For children, do not exceed 40 mg per kilogram of body weight in any 24-hour period. At 10 mg/kg per dose that works out to about 4 doses a day. For adults taking over-the-counter ibuprofen, the usual ceiling is 1,200 mg per day (for example, 400 mg three times daily) unless a doctor prescribes more.
Can I give ibuprofen by age instead of weight?
Age-based label charts are rough estimates. Weight-based dosing is more precise because body size varies widely within any age group, and giving the dose that matches the child's weight reduces the chance of under- or overdosing. If you do not know the child's weight, the closest label row is only a starting point — confirm with a pharmacist.
When should I not give ibuprofen?
Do not give ibuprofen to a child under 6 months without medical advice, and avoid it if the child is dehydrated, vomiting persistently, has a stomach ulcer, kidney disease, a bleeding disorder, or an allergy to NSAIDs. Fever that lasts more than a couple of days, or a fever with a stiff neck, rash, or lethargy, needs a doctor's evaluation rather than more medication.
How often can ibuprofen be repeated?
Ibuprofen may be repeated every 6 to 8 hours as needed. It should never be given more often than every 6 hours, and you should count the total doses so the 40 mg/kg/day ceiling is not exceeded. Spacing doses out also gives the stomach and kidneys time to recover.
Disclaimer
This ibuprofen dosage calculator is provided for informational purposes only and is not medical advice. Estimates are based on the standard weight-based mg/kg regimen and the common 100 mg/5 mL suspension strength; actual dosing depends on age, weight, medical history, other medications, and the exact product on your shelf. Doses are approximations and are not a substitute for professional care. Always follow the labeling on your specific bottle and confirm dosing with your pediatrician, pharmacist, or another qualified healthcare professional before giving any medication.