Pediatric Weight-Based Dose Calculator
Pediatric medication dosing is primarily weight-based. The standard formula is: single dose (mg) = prescribed dose in mg/kg multiplied by patient weight in kg. Clinicians then multiply by the number of doses per day to obtain total daily dose. When a liquid formulation is used, dividing the single dose by the drug concentration in mg/mL gives the volume to administer. This calculator handles all three steps. Always cross-check results against maximum dose limits in an authoritative pediatric reference. This tool is for educational and reference purposes only; all prescribing decisions must be made by qualified healthcare professionals.
Weight-based dosing formula
Single dose (mg) = mg/kg x weight (kg)
Daily dose (mg) = single dose x doses per day
Volume (mL) = single dose / concentration (mg/mL)
Always verify the calculated dose does not exceed the maximum single dose or daily dose for the specific drug and patient age group. Consult the drug's prescribing information or a pediatric formulary.
Important dosing considerations
- Maximum dose caps: Many drugs have a maximum that applies regardless of weight. Check each drug individually.
- Round sensibly: Doses are often rounded to the nearest practical volume (e.g., 0.1 mL in infants, 0.5 mL in older children).
- Neonates (0-28 days): Drug metabolism differs significantly; specialist guidance is essential.
- Obesity: Consider ideal body weight for some drugs to prevent dosing errors.
- Renal/hepatic impairment: Many drugs require dose adjustment when organ function is reduced.
Frequently asked questions
How is weight-based dosing calculated in children?
Pediatric dosing uses the formula: dose = mg/kg x weight. For example, if a drug is dosed at 10 mg/kg and the child weighs 20 kg, the single dose is 200 mg. Doses are usually given at defined intervals (every 8 hours, every 12 hours, etc.), and the prescriber must verify the dose against maximum single-dose and daily-dose limits.
Why is weight-based dosing used in children?
Children are not simply small adults. Drug distribution, metabolism, and clearance vary significantly with age and developmental stage. Weight-based dosing accounts for body size, which correlates with drug volume of distribution and clearance in most pediatric patients, particularly in infants and young children.
What weight should be used for pediatric dosing?
Actual body weight is typically used for normal-weight children. For obese children, the prescriber may use ideal body weight or adjusted body weight for some drugs to avoid toxicity. Neonates and premature infants have additional dosing complexities that require specialist input.
How do I calculate volume to administer from a concentration?
Volume (mL) = dose (mg) / concentration (mg/mL). For example, if the calculated dose is 200 mg and the available suspension is 250 mg/5 mL (50 mg/mL), the volume to give is 200 / 50 = 4 mL. This calculator performs this step when you enter the concentration.
Are there maximum dose limits to check?
Yes. Many pediatric drugs have maximum single-dose and daily-dose caps that should not be exceeded regardless of weight. Always verify calculated doses against the drug's prescribing information or a pediatric formulary such as the AAP Red Book or Harriet Lane Handbook.
Official sources
- American Academy of Pediatrics: Red Book: Report of the Committee on Infectious Diseases.
- FDA Pediatric Drug Information: Pediatric Drug Information.
Reviewed by the CalculatorHub team, edited by James Graham, 15 June 2026. See our methodology.