Pediatric Medication Dosage Calculator
Calculates a single-dose amount of common pediatric medications — acetaminophen, ibuprofen, or amoxicillin — based on a child's weight and daily dose frequency. Use it to double-check dosing before giving a child fever or pain relief.
About this calculator
Weight-based dosing is the standard approach in pediatrics because children's bodies metabolize drugs very differently from adults. The calculator multiplies the child's weight in kilograms by a per-kilogram dose factor — 15 mg/kg for acetaminophen, 10 mg/kg for ibuprofen, and 25 mg/kg for amoxicillin — then divides by the number of doses given per day to produce a single-dose amount in milligrams. Formula: dose per administration (mg) = round((weight × dosePerKg) / frequency × 100) / 100. For example, acetaminophen at 15 mg/kg for a 20 kg child dosed four times per day gives (20 × 15) / 4 = 75 mg per dose. These factors reflect widely cited pediatric guidelines but should always be verified against current prescribing information and confirmed by a qualified healthcare professional.
How to use
Example: a 15 kg child needs ibuprofen dosed three times per day. Dose factor for ibuprofen = 10 mg/kg. Single dose = (15 × 10) / 3 = 50 mg per administration. Now try acetaminophen for the same child given four times per day: (15 × 15) / 4 = 56.25 mg per dose. Always cross-reference with the concentration of the liquid suspension you have — if your acetaminophen suspension is 160 mg/5 mL, 56.25 mg corresponds to about 1.76 mL.
Frequently asked questions
How do you calculate the correct ibuprofen dose for a child by weight?
The standard pediatric ibuprofen dose is 10 mg per kilogram of body weight per dose. Multiply the child's weight in kg by 10 to get the total mg for one dose, then confirm this fits within the maximum single dose stated on the product label (often 400 mg). Doses are typically spaced 6–8 hours apart. Always use the measuring device that came with the product, and consult a pharmacist if the child is under 6 months.
What is the difference between acetaminophen and ibuprofen dosing for children?
Acetaminophen is dosed at approximately 15 mg/kg per dose and can be given every 4–6 hours, making it suitable for infants as young as 2 months. Ibuprofen is dosed at 10 mg/kg per dose every 6–8 hours but is generally not recommended for infants under 6 months or for children who are dehydrated. Because acetaminophen and ibuprofen work through different pathways, some clinicians recommend alternating them for persistent fever — always under medical guidance.
Why should pediatric medication doses be based on weight rather than age?
Children of the same age can vary dramatically in body mass, and drug distribution, metabolism, and elimination all scale with body size rather than birthday. An age-based flat dose risks underdosing a heavier child — leaving symptoms untreated — or overdosing a smaller child, which can cause toxicity. Weight-based dosing, capped at adult maximum doses, provides a much safer and more individualised estimate for each child.