Infant & Children's Tylenol Dosage Calculator
Estimate a weight-based acetaminophen dose for a child. Enter the child’s weight and age, then choose the product and check its strength against the label.
Estimate a Weight-Based Acetaminophen Dose
Children's Acetaminophen Dose Formula
Where:
- \(w\) — child’s weight in kilograms; pounds are converted to kilograms first.
- \(D_{\mathrm{low}}\) and \(D_{\mathrm{target}}\) — lower and upper ends of the weight-based range, in milligrams (mg).
- \(c\) — liquid concentration in milligrams per milliliter (mg/mL); the listed 160 mg per 5 mL liquid has \(c=32\).
- \(D\) — the measurable dose: \(D_{\mathrm{liquid}}\) or \(D_{\mathrm{tablet}}\), depending on the product.
- \(L\) — calculated daily acetaminophen limit in mg; \(N\) — maximum number of these measured doses in 24 hours. The floor brackets \(\lfloor\ \rfloor\) mean round down.
The calculator rounds a liquid dose down to a 0.5 mL increment or a chewable dose down to a half-tablet increment. It does not return a dose if that amount falls below 10 mg/kg.
Children's Acetaminophen Dose – Calculation Example
Example: A 4-year-old child weighs 16 kg, and the selected product is infant/children’s liquid containing 160 mg per 5 mL (32 mg/mL).
\[\begin{aligned}D_{\mathrm{low}}&=10(16)=160\text{ mg}\\D_{\mathrm{target}}&=15(16)=240\text{ mg}\\\text{Liquid volume}&=240/32=7.5\text{ mL}\\D&=7.5(32)=240\text{ mg}\\L&=75(16)=1200\text{ mg}\\N&=\min(5,\lfloor1200/240\rfloor)=5\end{aligned}\]
Result: The measurable dose is 7.5 mL, providing 240 mg. The calculated limit is 1,200 mg in 24 hours, or at most five of these doses, spaced at least 4 hours apart. Follow any stricter product-label or clinician instructions.
How to use the calculator
- Enter Child's weight and select Weight unit (kg or lb). Use a recent, measured weight when possible.
- Enter Child's age and select Age unit (months or years). For a child younger than 12 weeks, talk to a doctor before giving acetaminophen; the calculator uses three months as an approximation of that cutoff.
- Select Product. Compare its acetaminophen strength with the package label. If you choose Custom liquid concentration, enter the label’s strength in Custom concentration as mg/mL.
- Read Measurable dose together with Liquid volume or Chewable tablets. Check Weight-based range (10–15 mg/kg), the daily limit, maximum doses, and minimum time between doses before giving any medicine.
Understanding the dose estimate
Acetaminophen, called paracetamol in some countries, is used to reduce fever and relieve pain. A child’s dose is commonly estimated from body weight rather than age alone. This calculator starts with a 10–15 mg/kg range and aims for 15 mg/kg, capped at 1,000 mg per dose. Age is used as a safety check, not to calculate the milligram amount.
The Measurable dose may be below the target because the calculator rounds down to a volume or tablet fraction it can display. For liquids, Liquid volume is based on the selected concentration. For chewables, Chewable tablets assumes 160 mg per tablet and half-tablet increments. If rounding would produce less than 10 mg/kg, the calculator shows no dose rather than rounding up.
The Daily acetaminophen limit is the lesser of 75 mg/kg and 4,000 mg. Maximum doses in 24 hours is the lesser of five doses and the number of measured doses that fit under that calculated limit. These are ceilings, not a schedule or an instruction to give every possible dose. Count a rolling 24-hour period and include acetaminophen from every medicine the child receives.
Safety limits and practical checks
This estimate is not a prescription or a substitute for medical advice. Ask a doctor before giving acetaminophen to a child younger than 2 years. If a child is younger than 12 weeks, seek medical advice before giving it, particularly if the child has a fever. The calculator is limited to ages up to 18 years and weights from 1 to 100 kg; an accepted input does not establish that a product is appropriate for the child.
Check the package for the active ingredient, strength, age directions, dosing interval, and daily maximum. Products sold in different places may have different concentrations or instructions. Give doses at least 4 hours apart, but follow a longer interval or lower maximum if the label or a clinician specifies one. Do not combine cold, flu, or pain products without checking whether they also contain acetaminophen.
Measure liquid with an oral dosing syringe, not a kitchen spoon. Confirm that the syringe can measure the displayed volume. Do not split a chewable tablet unless its label or a pharmacist confirms that splitting is appropriate. If the displayed dose cannot be measured accurately, or the label conflicts with the estimate, ask a doctor or pharmacist instead of rounding up. Seek urgent medical advice for a suspected overdose, even if the child seems well.
For calculations involving a different prescribed liquid strength or tablet amount, see the Liquid Dose calculator or Tablet Dose calculator. Neither replaces the product label or advice from a clinician.
Frequently Asked Questions
How do I calculate a child’s acetaminophen dose by hand if their weight is in pounds?
First divide the weight in pounds by 2.205 to estimate kilograms. Multiply kilograms by 10 and 15 to find the usual milligram range per dose. For example, 22 lb is about 10 kg, giving a range of about 100–150 mg. To find a liquid volume, divide the chosen milligram dose by the bottle’s mg/mL strength. Check the label and ask a pharmacist if the volume is hard to measure.
How do I convert a label that says “mg per 5 mL” to mg/mL?
Divide the milligrams on the label by 5. A liquid labeled 160 mg per 5 mL contains 32 mg/mL. If the label uses another volume, divide by that volume instead. Read the complete label before calculating: products with similar names can have different strengths, and confusing milligrams with milliliters can cause a serious dosing error.
Should I give another dose if my child vomits after taking acetaminophen?
Do not automatically repeat the dose. Some medicine may already have been absorbed, even if vomiting happened soon afterward, and another full dose could be too much. Note when the medicine was given and when vomiting occurred, then ask a pharmacist or clinician whether and when another dose is appropriate. Seek medical advice if vomiting continues or your child seems unwell.
Can a child take acetaminophen and ibuprofen on the same day?
Sometimes, but use each medicine’s own dosing instructions and keep a written record to avoid mix-ups. Do not alternate them routinely unless a clinician advises it. Ibuprofen has different age restrictions and may be unsuitable for a child who is dehydrated or has certain medical conditions. Ask a clinician which medicine to use if you are unsure.
What if acetaminophen does not bring my child’s fever down?
A fever does not have to return to normal for the medicine to help; how your child looks, drinks, and behaves matters too. Do not give an extra dose or shorten the dosing interval. A baby younger than 3 months with a temperature of 100.4°F (38°C) or higher needs prompt medical assessment. Seek medical advice for breathing trouble, dehydration, unusual drowsiness, or worsening symptoms.
Can I use an adult acetaminophen tablet instead of a children’s product?
Do not substitute an adult tablet based on its name alone. Adult tablets may contain too much medicine for an accurately measurable child’s dose, and extended-release tablets must not be split or crushed unless their labeling specifically allows it. Ask a pharmacist or clinician to check the tablet strength, formulation, and an appropriate product for your child.
What should I do if my child may have had too much acetaminophen?
Contact a poison control center or seek urgent medical advice immediately, even if your child seems well; symptoms of an overdose can be delayed. Have the packages, product strengths, estimated amounts, and times taken ready. Do not wait for symptoms or give more acetaminophen while you seek advice. If your child is unconscious or having trouble breathing, call emergency services.