Infant Fever Dosage Calculator - Free Online Tool

Weight-based acetaminophen and ibuprofen dosing for babies and children

When your baby or young child develops a fever or pain, knowing the correct medication dose is one of the most important things you can do as a parent or caregiver. Unlike adults who typically take a standard pill, pediatric medication dosing is based on body weight — not age alone. Giving too little may be ineffective, while giving too much can be harmful. This Infant Fever Dosage Calculator uses the same weight-based formulas recommended by the American Academy of Pediatrics (AAP) and used by pediatricians worldwide. The two most common over-the-counter medications for infant and child fever and pain relief are acetaminophen (sold as Tylenol, Feverall, and generics) and ibuprofen (sold as Motrin, Advil, and generics). Each works differently: acetaminophen is safe from as early as 8–12 weeks of age (with physician guidance), while ibuprofen is only approved for infants 6 months and older. Knowing which medication to use, when, and in what dose can make the difference between effective relief and a dangerous mistake. Acetaminophen dosing for infants and children follows the AAP guideline of 10–15 milligrams per kilogram of body weight per dose, given every 4 to 6 hours as needed. The maximum number of doses is 5 in any 24-hour period, and the total daily dose must not exceed 75 mg/kg or 4,000 mg — whichever is lower. The current standard formulation is 160 mg per 5 mL (32 mg/mL) for both infants' and children's liquid suspensions, which simplifies dosing since the same product can be used across a wider age range. Ibuprofen dosing for children follows a guideline of 5–10 milligrams per kilogram of body weight per dose, given every 6 to 8 hours as needed. The maximum single dose is 600 mg, and the daily maximum is 40 mg/kg or 2,400 mg — whichever is lower. Ibuprofen must never be given to infants younger than 6 months or lighter than 7 kg (approximately 15.4 lbs). Because it is an anti-inflammatory, ibuprofen is generally considered more effective for fever reduction in older infants and children, but it should always be given with food or milk to reduce the risk of stomach upset. One of the most dangerous mistakes caregivers make is confusing medication formulations. Older concentrated infant drops (80 mg/mL) have largely been phased out in favor of the standardized 160 mg/5 mL suspension, but some products still vary. Always read the concentration label on your specific product and use only the dosing device provided — never a kitchen spoon. A teaspoon and a measuring syringe can hold very different amounts, and the difference can lead to significant over- or under-dosing. Fever itself is not a disease — it is the body's natural immune response to infection. Whether and when to treat a fever depends on the child's age, the temperature reading, and how the child appears. The AAP does not recommend treating every fever; a mildly elevated temperature in a child who is alert and drinking fluids may not need medication at all. However, fever in infants under 3 months of age is always a medical emergency requiring immediate evaluation. In children 3–6 months, a fever above 102.2°F (39°C) warrants a call to the pediatrician. For older infants and children, the focus should be on comfort — if the child is miserable, medication is appropriate regardless of the exact temperature number. This calculator displays a dosing range (minimum to maximum) rather than a single value to reflect the reality of clinical practice. The lower end (10 mg/kg for acetaminophen, 5 mg/kg for ibuprofen) is the safe starting dose, while the upper end represents the maximum recommended dose for full effect. For most situations, dosing in the middle of the range provides a good balance of efficacy and safety. For caregivers dealing with prolonged fevers or severe pain, some pediatricians recommend alternating acetaminophen and ibuprofen — giving one medication, then the other 3–4 hours later, cycling between them. This approach can help maintain more consistent fever control, but it should only be done under pediatrician guidance to avoid dosing errors or missing a maximum daily dose limit. Always keep a written log of which medication was given, how much, and when. Remember: this calculator provides educational dosing guidance based on published AAP standards. It does not replace a pediatrician's advice. If you are ever unsure about your child's medication, dose, or condition, contact your child's doctor or call Poison Control at 1-800-222-1222 (US).

Understanding Infant Fever Dosing

What Is Weight-Based Dosing?

Weight-based dosing is the medical standard for calculating pediatric medication amounts. Because infants and children have vastly different body sizes, a single fixed dose would be underdosing for heavier children and potentially dangerous for lighter infants. By calculating the dose as milligrams per kilogram of body weight (mg/kg), clinicians ensure that each child receives a proportionate and effective amount. This is the method used by the American Academy of Pediatrics, the FDA, and virtually every pediatric medical guideline worldwide. For acetaminophen, the standard is 10–15 mg/kg per dose; for ibuprofen, 5–10 mg/kg per dose.

How Is the Dose Calculated?

The dose is calculated in three steps. First, convert the child's weight to kilograms (divide pounds by 2.205). Second, multiply the weight in kg by the dose factor (e.g., 10 mg/kg for the minimum acetaminophen dose, 15 mg/kg for the maximum). Third, convert the milligram dose to milliliters using the formulation concentration (e.g., for 160 mg/5 mL suspension: mL = mg ÷ 32). For example, a child weighing 20 lbs (9.07 kg) would receive 91–136 mg of acetaminophen, or approximately 2.8–4.3 mL of the standard 160 mg/5 mL suspension per dose. Daily maximums are also calculated per kg and capped at absolute limits.

Why Dosing Accuracy Matters

Medication errors in children are a significant and preventable public health concern. Studies show that caregivers frequently give incorrect doses — both too little and too much — because of confusing label instructions, unfamiliar formulations, or misreading a dosing table. Acetaminophen overdose is one of the leading causes of acute liver failure in children in the United States. Ibuprofen overdose can cause kidney damage and gastrointestinal bleeding. At the same time, under-dosing leaves children in needless pain or allows fevers to climb. Using a calculator that accounts for actual body weight, formulation concentration, and safety limits dramatically reduces these risks.

Limitations and When to Call the Doctor

This calculator provides general dosing guidance based on published weight-based standards. It does not account for every clinical situation: children with liver disease should avoid acetaminophen; children with kidney disease or dehydration should avoid ibuprofen; premature infants may require hospital-level dosing adjustments. The calculator cannot evaluate whether medication is actually needed — that requires a clinical assessment. If your child has a fever under 3 months of age, difficulty breathing, a stiff neck, an unexplained rash, persistent vomiting, or is unusually lethargic, do not rely on this calculator — call your pediatrician or go to the emergency room immediately.

Pediatric Dosing Formulas

Acetaminophen Dose (per dose)

Dose = 10–15 mg/kg per dose

The AAP-recommended acetaminophen dosing range. Multiply the child's weight in kilograms by 10 (minimum dose) and 15 (maximum dose) to get the safe dose range in milligrams. Given every 4–6 hours, maximum 5 doses per 24 hours.

Ibuprofen Dose (per dose)

Dose = 5–10 mg/kg per dose

The AAP-recommended ibuprofen dosing range for children 6 months and older. Multiply the child's weight in kilograms by 5 (minimum dose) and 10 (maximum dose). Given every 6–8 hours, maximum 4 doses per 24 hours.

Volume from Dose

Volume (mL) = Dose (mg) / Concentration (mg/mL)

Converts a milligram dose to the volume to administer using the specific product concentration. For standard acetaminophen suspension (160 mg/5 mL = 32 mg/mL): mL = mg ÷ 32. For children's ibuprofen suspension (100 mg/5 mL = 20 mg/mL): mL = mg ÷ 20.

Maximum Daily Dose

Acetaminophen: max 75 mg/kg/day or 4,000 mg; Ibuprofen: max 40 mg/kg/day or 2,400 mg

The total medication given in 24 hours must not exceed these limits, whichever is lower. Exceeding acetaminophen daily limits risks liver damage; exceeding ibuprofen limits risks kidney injury and GI bleeding.

Pediatric Dosing Reference Tables

Acetaminophen Dosing by Weight (160 mg/5 mL Suspension)

Weight-based acetaminophen dosing chart using the standard 160 mg per 5 mL (32 mg/mL) oral suspension. Dose range: 10–15 mg/kg per dose, every 4–6 hours, max 5 doses/day.

Weight (lbs)	Weight (kg)	Dose Range (mg)	Volume Range (mL)	Max Daily Dose (mg)
6–11 lbs	2.7–5 kg	27–75 mg	0.8–2.3 mL	200–375 mg
12–17 lbs	5.5–7.7 kg	55–115 mg	1.7–3.6 mL	410–580 mg
18–23 lbs	8.2–10.4 kg	82–156 mg	2.6–4.9 mL	615–780 mg
24–35 lbs	10.9–15.9 kg	109–239 mg	3.4–7.5 mL	818–1,193 mg
36–47 lbs	16.3–21.3 kg	163–320 mg	5.1–10.0 mL	1,223–1,598 mg
48–59 lbs	21.8–26.8 kg	218–402 mg	6.8–12.6 mL	1,635–2,010 mg
60–71 lbs	27.2–32.2 kg	272–483 mg	8.5–15.1 mL	2,040–2,415 mg
72–95 lbs	32.7–43.1 kg	327–647 mg	10.2–20.2 mL	2,453–3,233 mg

Ibuprofen Dosing by Weight (100 mg/5 mL Suspension)

Weight-based ibuprofen dosing chart using children's 100 mg per 5 mL (20 mg/mL) oral suspension. Dose range: 5–10 mg/kg per dose, every 6–8 hours, max 4 doses/day. NOT for infants under 6 months or under 7 kg.

Weight (lbs)	Weight (kg)	Dose Range (mg)	Volume Range (mL)	Max Daily Dose (mg)
15–17 lbs	7–7.7 kg	35–77 mg	1.8–3.9 mL	280–308 mg
18–23 lbs	8.2–10.4 kg	41–104 mg	2.1–5.2 mL	328–416 mg
24–35 lbs	10.9–15.9 kg	55–159 mg	2.7–8.0 mL	436–636 mg
36–47 lbs	16.3–21.3 kg	82–213 mg	4.1–10.7 mL	652–852 mg
48–59 lbs	21.8–26.8 kg	109–268 mg	5.5–13.4 mL	872–1,072 mg
60–71 lbs	27.2–32.2 kg	136–322 mg	6.8–16.1 mL	1,088–1,288 mg
72–95 lbs	32.7–43.1 kg	164–431 mg	8.2–21.6 mL	1,308–1,724 mg

Dosage Calculation Examples

Infant Tylenol for an 18-lb, 6-Month-Old

A 6-month-old baby weighs 18 lbs. The parent has Infants' Tylenol oral suspension (160 mg per 5 mL). The baby has a fever of 101.5°F.

Convert weight: 18 lbs ÷ 2.205 = 8.16 kg

Minimum dose: 8.16 × 10 mg/kg = 81.6 mg

Maximum dose: 8.16 × 15 mg/kg = 122.4 mg

Concentration: 160 mg / 5 mL = 32 mg/mL

Volume range: 81.6 ÷ 32 = 2.6 mL to 122.4 ÷ 32 = 3.8 mL

Frequency: Every 4–6 hours as needed, max 5 doses in 24 hours

Max daily dose: 8.16 × 75 = 612 mg/day

Give 2.6 to 3.8 mL of Infants' Tylenol (160 mg/5 mL) per dose, every 4–6 hours as needed. Do not exceed 5 doses or 612 mg total in 24 hours. The fever of 101.5°F is a low-grade fever; medication can improve comfort but is not always required.

Children's Ibuprofen for a 25-lb Toddler

A 14-month-old toddler weighs 25 lbs and has a fever of 103°F. The parent has Children's Motrin oral suspension (100 mg per 5 mL).

Convert weight: 25 lbs ÷ 2.205 = 11.34 kg

Confirm age: 14 months — ibuprofen is safe (≥ 6 months)

Confirm weight: 11.34 kg — ibuprofen is safe (≥ 7 kg)

Minimum dose: 11.34 × 5 mg/kg = 56.7 mg

Maximum dose: 11.34 × 10 mg/kg = 113.4 mg

Concentration: 100 mg / 5 mL = 20 mg/mL

Volume range: 56.7 ÷ 20 = 2.8 mL to 113.4 ÷ 20 = 5.7 mL

Frequency: Every 6–8 hours as needed, max 4 doses in 24 hours

Max daily dose: 11.34 × 40 = 453.6 mg/day

Give 2.8 to 5.7 mL of Children's Motrin (100 mg/5 mL) per dose, every 6–8 hours as needed. Do not exceed 4 doses or 454 mg total in 24 hours. Give with food or milk. The fever of 103°F is a moderate-to-high fever; medication is recommended. Seek same-day medical attention if the fever does not respond.

Acetaminophen Chewable Tablets for a 50-lb Child

A 6-year-old child weighs 50 lbs and has a headache. The parent has Children's Tylenol chewable tablets (160 mg per tablet).

Convert weight: 50 lbs ÷ 2.205 = 22.68 kg

Minimum dose: 22.68 × 10 = 226.8 mg

Maximum dose: 22.68 × 15 = 340.2 mg

Tablets (160 mg each): 226.8 ÷ 160 = 1.4 tablets to 340.2 ÷ 160 = 2.1 tablets

Practical dose: 1.5 to 2 tablets per dose

Max daily dose: 22.68 × 75 = 1,701 mg (≈ 10.6 tablets/day)

Give 1.5 to 2 chewable tablets (160 mg each) per dose, every 4–6 hours as needed. This provides 240–320 mg per dose, within the safe 10–15 mg/kg range. Do not exceed 5 doses or approximately 10 tablets total in 24 hours.

How to Use This Calculator

Enter Your Child's Weight

Weigh your child accurately on a scale if possible. Enter the weight and toggle between lbs and kg. Dosing accuracy depends on having the correct weight — do not estimate if avoidable.

Enter Age and Select Medication

Optionally enter your child's age in months or years to activate critical safety alerts (ibuprofen is blocked under 6 months; acetaminophen triggers an emergency alert for infants under 3 months with fever). Then choose acetaminophen or ibuprofen.

Choose the Formulation

Select the specific formulation you have at home. The concentration (mg/mL) varies between products and determines the volume in mL. Check your product label and match it to the formulation shown.

Read the Dose Range and Safety Alerts

The calculator shows a minimum-to-maximum dose range in mL and mg, dosing frequency, daily maximum, and fever severity if a temperature was entered. Review all safety banners carefully before administering any medication.

Frequently Asked Questions

Why does this calculator show a dose range instead of a single number?

The dose range reflects the clinically accepted window recommended by the American Academy of Pediatrics: 10–15 mg/kg for acetaminophen and 5–10 mg/kg for ibuprofen. The lower end is a safe, effective starting dose for mild symptoms. The upper end provides maximum therapeutic effect for more severe pain or high fevers. Giving a dose anywhere within this range is considered safe. Most caregivers can use a dose in the middle of the range. Never exceed the upper end of the range or the absolute daily maximum.

Can I give acetaminophen and ibuprofen at the same time?

No — do not give both medications at the same time. However, some pediatricians recommend alternating them: give acetaminophen first, then give ibuprofen 3–4 hours later, then repeat the cycle. This approach can help maintain more consistent fever control for persistent high fevers. Because each medication has its own daily maximum limit, you must track doses of each separately and never exceed those limits. Alternating should only be done under the guidance of your child's pediatrician, as keeping track of two medications simultaneously increases the risk of dosing errors.

My baby is 5 months old. Why is ibuprofen blocked?

Ibuprofen is not approved by the FDA for use in infants younger than 6 months of age. This restriction exists because very young infants' kidneys are not mature enough to safely process ibuprofen, creating a risk of kidney damage. Additionally, research on ibuprofen safety and efficacy has not been conducted in infants under 6 months. For infants in the 0–5 month range with fever or discomfort, acetaminophen (with age-appropriate caution) is the only recommended over-the-counter option — always consult your pediatrician before giving any medication to an infant this young.

What is the difference between Infants' Tylenol and Children's Tylenol?

As of 2011, the FDA standardized acetaminophen products so that Infants' Tylenol Oral Suspension and Children's Tylenol Oral Suspension now share the same concentration: 160 mg per 5 mL (32 mg/mL). This change was made specifically to reduce the risk of accidental overdose from confusing two products with different concentrations. Previously, infants' drops were more concentrated (80 mg/mL). Always verify the concentration on your specific product label — some older products may still be in home medicine cabinets, and product formulations outside the US may differ.

When should I NOT treat a fever with medication?

The American Academy of Pediatrics advises that the purpose of treating fever is to improve your child's comfort, not to normalize the temperature number. Fever itself is a healthy immune response. If your child has a mild fever (100.4–102°F) but is alert, playful, drinking fluids, and not appearing distressed, medication may not be necessary. You should always treat fever in infants under 3 months of age as a medical emergency and seek care — do not give medication and wait. In older children, focus on the child's behavior and comfort level rather than the thermometer reading.

What should I do if I think I gave too much medication?

If you believe you may have given your child too much acetaminophen or ibuprofen, act immediately — do not wait for symptoms to appear. Call Poison Control at 1-800-222-1222 (United States) right away. They are available 24 hours a day, 7 days a week and can advise you on whether emergency care is needed. Early treatment of acetaminophen overdose is critical — liver damage may not be apparent for 24–72 hours, and the antidote is most effective when given early. Signs of overdose include nausea, vomiting, extreme sleepiness, and abdominal pain, but symptoms may initially be absent.