This is an educational reference tool only. Dose calculations must be verified against your local formulary, the patient's clinical status, and current institutional guidelines before administration.
This tool covers oral dosing only. Do not use these doses for IV or IM routes without consulting appropriate references.
Weight-based dosing errors are among the most frequent and preventable medication mistakes in pediatrics, with small rounding errors translating into clinically significant overdoses or underdoses.
Unit confusion between mg/kg/day and mg/kg/dose is a persistent source of error — the same drug can look very different depending on how the dose is expressed.
Formulation mismatches occur when the calculated milligram dose does not align with available syrup concentrations or tablet strengths, requiring an extra conversion step that introduces additional risk.
Maximum dose ceilings are frequently overlooked, particularly in heavier children, where the weight-based calculation may exceed the adult cap.
Frequency errors — using a TID dose for a BID regimen, or vice versa — can result in significant under- or over-treatment even when the per-dose calculation is correct.
The calculator accepts the child's weight (in kg, g, or lb) and age, then applies validated mg/kg dosing rules for a selected medication. The result is expressed both in milligrams and in the volume of the chosen formulation (e.g., mL of syrup), removing the manual two-step conversion that leads to most errors.
Each drug in the reference list carries its own dosing range, maximum single dose, maximum daily dose, and available formulations. When a weight-based calculation would exceed the adult cap, the tool automatically applies the ceiling and flags the rounding with a visible warning.
A Drug Reference tab provides at-a-glance summaries of category, dosing range, frequency, clinical notes, and contraindications — so prescribers can cross-check the calculator output against the clinical picture without leaving the screen.
The Dose Comparison tab allows a single weight entry to generate side-by-side calculated doses for all drugs in the reference list simultaneously, which is particularly useful when selecting between therapeutic alternatives at the bedside.
Every result includes a daily dose in addition to the per-dose figure, helping clinicians confirm total daily exposure stays within safe limits — especially important for paracetamol and other drugs with narrow daily ceilings.
A calculation history is stored within the session and can be exported to CSV or copied to the clipboard, supporting documentation in clinical notes and medication review.
Pediatric weight-based dosing uses a straightforward proportional formula, but each component must be applied carefully to avoid compounding errors.
The core formula is applied in three steps:
Amoxicillin is a first-line beta-lactam antibiotic for respiratory, ear, and urinary tract infections. The standard oral dose is 20–50 mg/kg/day divided TID, with a single-dose maximum of 500 mg and a daily ceiling of 3,000 mg. Available as syrup 250 mg/5 mL or tablets of 250 mg and 500 mg.
Amoxicillin-Clavulanate (Augmentin) is reserved for infections caused by beta-lactamase-producing organisms. Dosing is based on the amoxicillin component — 45 mg/kg/day divided BID — with a maximum of 875 mg per dose. The clavulanate component should not exceed 10 mg/kg/day to minimise GI adverse effects.
Paracetamol (Acetaminophen) is the first-line analgesic and antipyretic for children. The dose is 10–15 mg/kg per dose every 4–6 hours, with a maximum of 4 doses per day and a strict daily ceiling of 4,000 mg. Clinicians must check all other products the child is receiving for hidden paracetamol to prevent double-dosing.
Ibuprofen is an NSAID used for pain and fever in children aged over 3 months and weighing more than 5 kg. The dose is 5–10 mg/kg per dose every 6–8 hours, not exceeding 400 mg per dose or 1,200 mg/day. It should always be given with food and avoided in dehydration, renal impairment, or NSAID-sensitive asthma.
Always weigh the child at the time of prescribing — estimated or recalled weights introduce systematic error that compounds through every step of the weight-based calculation.
Renal and hepatic impairment can significantly alter drug clearance in children. Amoxicillin and ibuprofen require dose reduction or avoidance in renal impairment; paracetamol requires caution in hepatic disease. The calculator does not adjust for organ impairment — this must be done separately.
Age restrictions apply to several drugs in the list. Ibuprofen is not recommended below 3 months. Augmentin is typically reserved for specific microbiological indications and not used routinely in neonates without specialist guidance.
Double-check the formulation concentration before drawing up a dose. A child who receives a dose calculated for 250 mg/5 mL syrup but is given 125 mg/5 mL syrup will receive half the intended dose — a common but avoidable error.
A pediatric dose calculator is most valuable in time-pressured clinical environments — emergency departments, walk-in clinics, and inpatient wards — where mental arithmetic increases error risk and a reliable reference is needed within seconds.
It is equally useful in community pharmacy for verifying prescriptions, in nursing education for teaching weight-based concepts, and at home for caregivers who have been instructed by a clinician to administer a specific mg/kg dose of an over-the-counter medication.
The tool does not replace clinical judgment. It provides a calculated starting point; the final decision on dose, route, frequency, and duration always rests with the licensed prescriber who knows the full clinical picture.
| Weight (kg) | Amoxicillin (mg) | Paracetamol (mg) | Ibuprofen (mg) | Prednisolone* (mg) |
|---|---|---|---|---|
| 5 kg | 100 mg | 75 mg | 50 mg | 5 mg |
| 8 kg | 160 mg | 120 mg | 80 mg | 8 mg |
| 10 kg | 200 mg | 150 mg | 100 mg | 10 mg |
| 12 kg | 240 mg | 180 mg | 120 mg | 12 mg |
| 15 kg | 300 mg | 225 mg | 150 mg | 15 mg |
| 20 kg | 400 mg | 300 mg | 200 mg | 20 mg |
| 25 kg | 500 mg | 375 mg | 250 mg | 25 mg |
| 30 kg | 500 mg | 450 mg | 300 mg | 30 mg |
| 35 kg | 500 mg | 525 mg | 350 mg | 35 mg |
| 40 kg | 500 mg | 600 mg | 400 mg | 40 mg |
| 50 kg | 500 mg | 750 mg | 400 mg | 40 mg |
Keep calculating
Usman Shaoukat is the founder and editor of BestMedCal. He is a computer and web specialist who researches every BestMedCal tool from published standards and medication-safety references, including NIST, the U.S. FDA, NCBI and the American Academy of Pediatrics. His focus is dose-to-volume calculations and unit conversions. Every formula and worked example is checked against the sources listed on each page. BestMedCal has no clinicians on staff: our tools check arithmetic and explain methods; they do not recommend doses. If you spot an error, contact us and we will review it.