Calculate safe pediatric doses by weight and age
Every parent has faced the stressful moment of a sick child in the middle of the night — searching through dosing charts, trying to remember the right amount of Tylenol or Motrin. The Child Medication Dosage Calculator takes that guesswork out of the equation. By entering your child's weight and age, you can instantly see the appropriate dose in milliliters, teaspoons, or tablets for the most commonly used over-the-counter pediatric medications. Accurate pediatric dosing is critical. Children are not simply small adults — their bodies process medications differently, and the correct dose depends primarily on body weight. An under-dose may be ineffective, failing to relieve fever or discomfort. An accidental overdose, especially of acetaminophen, can cause serious liver damage. This calculator uses established weight-based dosing formulas recommended by pediatric healthcare organizations to help you arrive at the right dose for your specific child. This tool covers the five most common OTC pediatric medications: Acetaminophen (Tylenol) for fever and pain at 15 mg per kilogram per dose; Ibuprofen (Motrin/Advil) for fever and inflammation at 7.5 mg/kg per dose; Diphenhydramine (Benadryl) for allergic reactions at 1 mg/kg per dose; Cetirizine (Zyrtec) for seasonal allergies using age-based dosing; and Loratadine (Claritin) for non-drowsy allergy relief. For each medication, the calculator shows the dose in multiple formats — milliliters (mL), teaspoons (tsp), and tablet counts — so you can match whatever form you have at home. Beyond a single dose, this calculator helps with safe medication management. The next-dose timer tells you when you can safely give the next dose based on how long ago the last dose was given. The alternating acetaminophen and ibuprofen scheduler — a common pediatric practice recommended by many doctors for high fevers — shows a sample staggered dosing schedule so you can use both medications safely without exceeding daily limits. A visual dose safety chart shows where the calculated dose falls relative to the maximum single dose, giving you an at-a-glance safety indicator. Important safety information is built into every calculation. Age and weight restrictions are enforced automatically — ibuprofen is flagged as not recommended for children under 6 months, diphenhydramine for children under 2 years. Important notes like giving ibuprofen with food and the drowsiness warning for diphenhydramine are displayed alongside results. The Poison Control hotline (1-800-222-1222) is prominently displayed throughout the tool. This calculator is intended as an educational reference for parents and caregivers. It uses standard weight-based dosing guidelines from sources including AAP HealthyChildren.org, St. Louis Children's Hospital, and multiple pediatric practice resources. However, it does not replace the advice of your child's pediatrician or pharmacist. Always confirm doses with your healthcare provider, especially for infants under 3 months, children with medical conditions, or when combining with other medications. When in doubt, call your doctor.
Understanding Pediatric Medication Dosing
What Is Weight-Based Dosing?
Weight-based dosing is the standard method for calculating medication amounts in children. Unlike adults, where a standard 500 mg tablet is appropriate for nearly everyone, children vary enormously in body size — a 15-pound infant and a 60-pound child need very different doses. The formula is straightforward: multiply the child's weight in kilograms by the dose in milligrams per kilogram (mg/kg). For acetaminophen, the recommended dose is 15 mg/kg per dose. For ibuprofen, it is 7.5 mg/kg. For diphenhydramine, it is 1 mg/kg. Once you have the milligram dose, you divide by the concentration of the liquid (in mg/mL) to get the volume to measure. This is why weight-based dosing produces more accurate results than age-based charts, which can significantly under- or over-dose children at the extremes of a weight range.
How Are Doses Calculated?
The core formula for weight-based pediatric dosing has two steps. First, calculate the dose in milligrams: Dose (mg) = Weight (kg) × Dose per kg (mg/kg). For example, a 10 kg child receiving acetaminophen at 15 mg/kg gets 150 mg per dose. Second, convert to a volume if using a liquid: Volume (mL) = Dose (mg) ÷ Concentration (mg/mL). Standard children's acetaminophen liquid is 160 mg per 5 mL (32 mg/mL), so 150 mg ÷ 32 mg/mL = 4.69 mL. Doses are rounded to practical increments. For antihistamines like cetirizine and loratadine, dosing is age-based rather than weight-based, with set amounts for age groups 2–5, 6–11, and 12+. All calculations enforce maximum single-dose limits to prevent overdose.
Why Accurate Dosing Matters
Medication errors are one of the most common causes of accidental poisoning in children. The American Association of Poison Control Centers receives tens of thousands of calls related to children's medication accidents each year. Two specific risks are most common: under-dosing because parents are afraid to give 'too much,' resulting in ineffective treatment of fever or pain; and over-dosing because parents use outdated dosing charts, use a kitchen spoon instead of an oral syringe, or unknowingly give a second medication that also contains acetaminophen (such as certain cold medicines). This calculator helps address both risks by providing an accurate, weight-based dose and by always displaying maximum limits alongside the calculated dose. Always use the calibrated oral syringe or dosing cup that comes with the medication — kitchen teaspoons can vary significantly from the standard 5 mL.
Limitations and Safety Notes
This calculator provides general dosing guidance based on widely accepted pediatric standards and is intended for informational purposes only. It should not replace the advice of a qualified healthcare provider. Several situations require direct consultation with a doctor: infants under 3 months with any fever, children under 6 months needing ibuprofen, any child with liver or kidney disease, children taking other medications that may interact, and any situation where the child's condition appears serious. Diphenhydramine (Benadryl) causes drowsiness and can paradoxically cause excitability in some young children — it is not recommended for routine use in children under 2 years for allergies or any age for cold symptoms. The alternating acetaminophen/ibuprofen schedule shown is a common practice but should be confirmed with your pediatrician. In the event of a suspected overdose, call Poison Control immediately at 1-800-222-1222 (US).
Fórmulas
The standard pediatric dosing formula. Acetaminophen uses 15 mg/kg per dose, ibuprofen uses 7.5 mg/kg per dose (some sources use 5–10 mg/kg), and diphenhydramine uses 1–1.25 mg/kg per dose. The calculated mg dose is then capped at the maximum single dose for the medication.
Converts the milligram dose to a measurable liquid volume. Standard concentrations: Children's acetaminophen is 160 mg/5 mL (32 mg/mL), children's ibuprofen is 100 mg/5 mL (20 mg/mL), and children's diphenhydramine is 12.5 mg/5 mL (2.5 mg/mL).
Since all pediatric dose calculations use kilograms, weights entered in pounds must be converted first. For quick estimation, divide pounds by 2.2.
Acetaminophen maximum is 75 mg/kg/day (up to 4,000 mg/day for teens). Ibuprofen maximum is 40 mg/kg/day (up to 1,200 mg/day). Diphenhydramine maximum is 5 mg/kg/day (up to 300 mg/day). Each dose must not exceed the single-dose maximum, and daily totals must not exceed these limits.
Reference Tables
Acetaminophen (Tylenol) Dosing by Weight
| Peso (lbs) | Peso (kg) | Dose (mg) | Children's Liquid (160mg/5mL) | Chewable 80mg Tabs |
|---|---|---|---|---|
| 12–17 | 5.4–7.7 | 80 mg | 2.5 mL | 1 tab |
| 18–23 | 8.2–10.4 | 120 mg | 3.75 mL | 1.5 tabs |
| 24–35 | 10.9–15.9 | 160 mg | 5 mL | 2 tabs |
| 36–47 | 16.3–21.3 | 240 mg | 7.5 mL | 3 tabs |
| 48–59 | 21.8–26.8 | 320 mg | 10 mL | 4 tabs |
| 60–71 | 27.2–32.2 | 400 mg | 12.5 mL | 5 tabs |
| 72–95 | 32.7–43.1 | 480 mg | 15 mL | 6 tabs |
Ibuprofen (Motrin/Advil) Dosing by Weight (6 months+)
| Peso (lbs) | Peso (kg) | Dose (mg) | Children's Liquid (100mg/5mL) | Chewable 50mg Tabs |
|---|---|---|---|---|
| 12–17 | 5.4–7.7 | 50 mg | 2.5 mL | 1 tab |
| 18–23 | 8.2–10.4 | 75 mg | 3.75 mL | 1.5 tabs |
| 24–35 | 10.9–15.9 | 100 mg | 5 mL | 2 tabs |
| 36–47 | 16.3–21.3 | 150 mg | 7.5 mL | 3 tabs |
| 48–59 | 21.8–26.8 | 200 mg | 10 mL | 4 tabs |
| 60–71 | 27.2–32.2 | 250 mg | 12.5 mL | 5 tabs |
| 72–95 | 32.7–43.1 | 300 mg | 15 mL | 6 tabs |
Worked Examples
Acetaminophen Dose for a 30-lb Child
Convert weight to kg: 30 lbs ÷ 2.205 = 13.6 kg
Calculate mg dose: 13.6 kg × 15 mg/kg = 204 mg
Check against maximum single dose: 204 mg < 480 mg max — OK
Calculate liquid volume: 204 mg ÷ 32 mg/mL = 6.4 mL
Convert to teaspoons: 6.4 mL ÷ 5 = 1.3 tsp
Ibuprofen Dose for a 44-lb Child
Convert weight to kg: 44 lbs ÷ 2.205 = 20.0 kg
Calculate mg dose: 20.0 kg × 7.5 mg/kg = 150 mg
Check against maximum single dose: 150 mg < 400 mg max — OK
Calculate liquid volume: 150 mg ÷ 20 mg/mL = 7.5 mL
Convert to teaspoons: 7.5 mL ÷ 5 = 1.5 tsp
Alternating Acetaminophen and Ibuprofen Schedule
Calculate Tylenol dose: 22 kg × 15 mg/kg = 330 mg
Calculate Motrin dose: 22 kg × 7.5 mg/kg = 165 mg
8:00 AM — Tylenol 330 mg
11:00 AM (3 hours later) — Motrin 165 mg
2:00 PM (3 hours later) — Tylenol 330 mg
5:00 PM (3 hours later) — Motrin 165 mg
8:00 PM (3 hours later) — Tylenol 330 mg
Como Usar Esta Calculadora
Enter Your Child's Weight
Weigh your child on a scale and enter the value. Toggle between pounds and kilograms using the unit button. Use your most recent accurate weight — dosing accuracy depends on an up-to-date weight, especially for infants who gain weight rapidly.
Enter Age and Select Medication
Enter your child's age in years and months. Age is used to check age-based restrictions — for example, ibuprofen is not recommended under 6 months, and diphenhydramine (Benadryl) is not recommended for children under 2 years. Then select the medication you want to give from the dropdown.
Choose the Formulation
Select the specific product form you have at home — Children's Liquid, Chewable Tablets, or Adult Tablets. The calculator automatically uses the correct concentration for each formulation. Children's liquid acetaminophen is 160 mg per 5 mL; children's liquid ibuprofen is 100 mg per 5 mL.
Read the Results and Print
Review the dose in mL and teaspoons (for liquids) or tablet count. Check the safety chart to confirm the dose is within the therapeutic range. Optionally enter how many hours ago the last dose was given to see when the next dose is safe. Use the Print Card button to save a printed reference for nighttime use.
Perguntas Frequentes
Can I give acetaminophen and ibuprofen at the same time?
No — you should not give them at exactly the same time, but many pediatricians recommend alternating them for high or persistent fevers. Because acetaminophen and ibuprofen work differently, alternating them can help keep fever under control longer than using just one. A common schedule is to give one medication, then the other 3 hours later, continuing to alternate every 3 hours. However, this approach should always be discussed with and confirmed by your pediatrician before trying it — it is not appropriate for all children, and you must track each dose carefully to avoid exceeding daily limits for either medication.
Why is ibuprofen not recommended for babies under 6 months?
The FDA restricts ibuprofen use to children 6 months and older because infants' kidneys are not mature enough to safely process NSAIDs (non-steroidal anti-inflammatory drugs) like ibuprofen. In very young infants, ibuprofen can cause kidney injury and has not been established as safe. For fever management in infants under 6 months, acetaminophen (Tylenol) is the recommended OTC option — but any fever in a baby under 3 months should prompt an immediate call to your doctor, as it may indicate a serious infection requiring medical evaluation.
Why should I use a syringe instead of a teaspoon?
Kitchen teaspoons vary widely in actual volume — anywhere from 3 mL to 7 mL depending on the spoon. The standard measurement teaspoon is 5 mL, but a typical kitchen spoon may hold significantly more or less. For liquid medications, even small measurement errors can mean under-dosing (ineffective) or over-dosing (potentially harmful). Always use the oral dosing syringe or calibrated cup that comes with the medication. If you do not have one, ask your pharmacist for a free oral syringe — they are widely available. Oral syringes allow accurate measurement to the nearest 0.1 mL.
What should I do if I accidentally gave too much?
If you believe you have given too much of any medication to your child, contact Poison Control immediately at 1-800-222-1222 (US), available 24 hours a day, 7 days a week. Do not wait for symptoms to appear — acetaminophen overdose, for example, may not show symptoms for 24 hours but can cause serious liver damage if not treated promptly. If your child is unconscious, having difficulty breathing, or having seizures, call 911 immediately. Keep the medication bottle handy when you call so you can report the exact product, concentration, and amount given.
Does Benadryl (diphenhydramine) help with colds in children?
No. Studies have consistently shown that diphenhydramine and other antihistamines do not reduce cold symptoms in children and are not recommended for colds in children under 4 years. The American Academy of Pediatrics (AAP) advises against using over-the-counter cold and cough medications in children under 4 years of age because they are ineffective and can cause side effects including sedation, paradoxical excitability, rapid heart rate, and difficulty urinating. Diphenhydramine is appropriate for allergic reactions and hives in children 2 years and older but should be used with caution and under a doctor's guidance.
What is the difference between Zyrtec and Claritin for kids?
Both cetirizine (Zyrtec) and loratadine (Claritin) are second-generation antihistamines used to treat seasonal allergies, hives, and runny nose in children 2 years and older. The main difference is that cetirizine may cause drowsiness in some children, while loratadine is considered non-drowsy for most children. Both are dosed once daily. For ages 2–5, cetirizine is 2.5 mg and loratadine is 5 mg. For ages 6–11, cetirizine is 5 mg and loratadine is 5 mg. Ages 12 and up receive 10 mg of either medication. Neither medication has approved weight-based dosing — they are dosed by age group. If your child's allergies are severe or not controlled by one antihistamine, consult your pediatrician for alternatives.