Pediatric dose calculator (mg/kg)
Enter the child's weight, the ordered dose in mg/kg/day, and how many doses it's divided into. Weight can be in pounds or kilograms.
For studying and practice only. This isn't a clinical tool: always follow the prescriber's order, your pharmacist, and your facility's policies.
How weight-based dosing works
kg = lb ÷ 2.2 → mg/day = kg × mg/kg/day → mg per dose = mg/day ÷ doses per day
Worked example
A 55 lb child is ordered 20 mg/kg/day divided every 12 hours
- 55 lb ÷ 2.2 = 25 kg
- 25 kg × 20 mg/kg/day = 500 mg/day
- every 12 hours = 2 doses → 500 ÷ 2 = 250 mg per dose
Read the order carefully: "divided every 8 hours" means 3 doses a day, and "every 6 hours" means 4. If the order is written per dose (mg/kg/dose), skip the division.
Practice these calculations the way the PTCB exam asks them
Try free PTCE practice questions on order entry and processing, including weight-based dosing and NDC conversion, with explanations. No signup.
Practice calculation questions freeFrequently asked questions
- How do you calculate a pediatric dose in mg/kg?
- Convert the weight to kilograms (pounds ÷ 2.2), multiply by the ordered mg/kg/day to get the total mg per day, then divide by the number of doses per day to get mg per dose.
- Why divide pounds by 2.2?
- One kilogram is about 2.2 pounds (2.2046, exactly). Pharmacy calculations, including PTCE practice questions, use 2.2.
- What's the difference between mg/kg/day and mg/kg/dose?
- mg/kg/day is the total for the whole day and has to be divided by the number of doses. mg/kg/dose is already per dose, so you multiply by the weight and stop there. Mixing them up multiplies or divides the dose by the number of doses per day.
- Can I use this for real patients?
- No. It's a study tool. Real pediatric doses are checked against maximum doses and clinical factors by a pharmacist and the prescriber.