Pediatric Dose Calculator — mg/kg Dosage by Weight for Children (mg & μg)

Pediatric Dose Calculator

The pediatric dose calculator is a simple tool for computing the pediatric dosage for a child of a given weight. 👶 Our calculator allows you to convert values in mg or μg to a precise volume of the medication, using a wide range of units.

How to Use the Pediatric Dose Calculator?

Pediatric dosage is a complicated matter — we decided to make things easier for you with a step-by-step guide:

1. Select the dose unit — choose mg (milligrams) or μg (micrograms). Note: 1 mg = 1,000 μg.
2. Choose the dosage type — your prescribed dose may be given as:
   • mg/kg/day — per kilogram of body weight per day (most common)
   • mg/kg/dose — per kilogram of body weight per single dose
   • mg/day — fixed total daily dose (no weight needed)
   • mg/dose — fixed dose per single administration (no weight needed)
3. Enter the dose amount — the numeric value of the prescribed dose (e.g., 15 for 15 mg/kg/day).
4. Select the frequency — how often the medication is given. See the abbreviation table below.
5. Enter the child's weight — in kg (metric) or lbs (imperial). Required for weight-based dose types only.
6. Enter the drug concentration — the amount of active ingredient per unit volume or solid:
   • mg/ml — liquid suspension (e.g., 50 mg/ml)
   • mg/5ml — liquid suspension by teaspoon (e.g., 250 mg/5ml)
   • mg/tablet — solid tablet form
   • mg/capsule — capsule form
7. Click Calculate — the results will show your dose per administration, total daily dose, and the volume or number of tablets needed.

💡 Our mg per kg dosage calculator works both ways — you may convert the medication's weight to volume and the other way around.

Dose Frequency Abbreviations

How Do You Calculate Pediatric Doses?

The most common method for calculating pediatric medication doses is the weight-based (mg/kg) method. Here are the key formulas:

Formula 1: mg/kg/day → dose per administration

Daily Dose (mg) = Dose (mg/kg/day) × Weight (kg)
Dose per Administration (mg) = Daily Dose ÷ Number of Doses per Day
Volume per Dose (ml) = Dose per Administration ÷ Drug Concentration (mg/ml)

Formula 2: mg/kg/dose → daily total

Dose per Administration (mg) = Dose (mg/kg/dose) × Weight (kg)
Daily Total (mg) = Dose per Administration × Number of Doses per Day

Unit Conversions

• 1 mg = 1,000 μg (micrograms)
• 1 kg = 2.20462 lbs
• 1 ml = 0.033814 fl oz (US fluid ounces)
• 1 tsp = 5 ml

Child Dose Calculation Examples

Example 1 (Metric): Amoxicillin 40 mg/kg/day, BID, child 20 kg, suspension 250 mg/5ml

1. Daily dose = 40 × 20 = 800 mg/day
2. Dose per administration = 800 ÷ 2 = 400 mg
3. Volume per dose = (400 ÷ 250) × 5 = 8 ml per dose

Example 2 (Imperial): Ibuprofen 10 mg/kg/dose, TID, child 44 lbs, suspension 100 mg/5ml

1. Weight in kg = 44 ÷ 2.20462 ≈ 19.96 kg
2. Dose per administration = 10 × 19.96 ≈ 199.6 mg
3. Daily total = 199.6 × 3 ≈ 598.8 mg/day
4. Volume per dose = (199.6 ÷ 100) × 5 ≈ 9.98 ml ≈ 10 ml per dose

Example 3 (μg): Folic acid 50 μg/kg/day, QD, child 15 kg, tablet 400 μg

1. Daily dose = 50 × 15 = 750 μg/day
2. Dose per administration (QD) = 750 μg
3. Tablets per dose = 750 ÷ 400 ≈ 1.875 tablets (round to 2 under physician guidance)

Frequently Asked Questions (FAQs)

What is the most common pediatric dosing method?

The weight-based method (mg/kg) is the gold standard for pediatric dosing. It accounts for the child's body size, which affects how drugs are absorbed, distributed, metabolized, and excreted.

What is the difference between mg/kg/day and mg/kg/dose?

mg/kg/day is the total daily dose per kilogram, which you then divide by the number of administrations per day to find the per-dose amount. mg/kg/dose is already the per-dose amount per kilogram — multiply it by weight to get the dose, then by frequency to get the daily total.

What does BID mean in pediatrics?

BID (from Latin bis in die) means twice daily — the medication is given 2 times per day, typically every 12 hours (e.g., morning and evening).

How do I calculate tablet doses for children?

Select mg/tablet as the concentration unit. Enter the strength of each tablet (e.g., 500 for a 500 mg tablet). The calculator will show how many tablets per dose. Tablets are often split or crushed for children — consult your pharmacist.

Can I use this calculator for μg (microgram) doses?

Yes! Select μg (micrograms) as the dose unit. All calculations will be performed in micrograms. This is useful for medications like vitamins, hormones, or highly potent drugs where doses are very small.

Is this calculator suitable for newborns?

Neonatal dosing (newborns under 28 days) follows different pharmacokinetic principles and often requires specialist calculation. This calculator is best suited for infants (1–12 months) and children (1–18 years). Always consult a neonatologist or pediatrician for newborn dosing.

What is PRN dosing?

PRN (from Latin pro re nata) means as needed. The medication is given only when required (e.g., fever, pain), not on a fixed schedule. For PRN calculations, use the mg/dose dosage type.