Medication Dosage Calculator
Calculate accurate medication dosages based on patient weight, age, and medication concentration.
DISCLAIMER: This calculator is for informational purposes only. Always consult with a healthcare professional before administering any medication. Double-check all calculations with a healthcare provider. This tool does not replace professional medical advice.
Dosage Results
Total Daily Dose:
Single Dose:
Administration Amount:
Body Surface Area:
Total Daily Dose:
Creatinine Clearance:
Renal Function:
Recommended Dosage Adjustment:
About Medication Dosage Calculation
Accurate medication dosing is crucial for effective treatment and patient safety. Our dosage calculator provides estimates for various dosing methods based on patient characteristics and medication information.
Common Dosage Calculation Methods
Weight-Based Dosing (mg/kg)
Weight-based dosing calculates medication amounts based on a patient's weight. This is the most common method, especially for pediatric patients and medications with a narrow therapeutic index.
Formula: Dose (mg) = Weight (kg) × Dosage (mg/kg)
Body Surface Area (BSA)
BSA dosing accounts for both weight and height, making it particularly useful for certain medications, including many chemotherapy drugs.
Mosteller Formula: BSA (m²) = √[(Height (cm) × Weight (kg))/3600]
Dose = BSA (m²) × Dosage (mg/m²)
Creatinine Clearance
For medications eliminated by the kidneys, dosing may need adjustment based on renal function, which is commonly assessed through creatinine clearance calculations.
Cockcroft-Gault Formula: CrCl = [(140 - Age) × Weight (kg)] / [72 × Serum Creatinine (mg/dL)] × (0.85 if female)
Pediatric Dosing Considerations
Medication dosing for children requires special attention due to differences in metabolism, body composition, and organ development. Most pediatric medications are dosed by weight (mg/kg) or body surface area (mg/m²), rather than using fixed adult doses.
Important considerations include:
- Lower body fat percentage in children affects drug distribution
- Immature liver and kidney function can affect medication metabolism and excretion
- Age-specific dosing protocols for many medications
- Maximum dose limits that should not be exceeded even with weight-based calculations
Ensuring Medication Safety
While calculators provide helpful estimates, safe medication administration requires additional precautions:
- Always verify calculations, especially for high-risk medications
- Consider the "Rule of 6" for continuous infusions in pediatrics
- Use appropriate measuring devices (oral syringes for liquid medications)
- Consider patient-specific factors that may affect dosing
- Follow established protocols for high-alert medications
IMPORTANT: This calculator is for estimation purposes only. Always consult with a pharmacist or healthcare provider to verify dosage calculations before administering any medication.
Frequently Asked Questions
What is the difference between mg/kg and mg/m² dosing?
Weight-based dosing (mg/kg) calculates medication doses solely based on the patient's weight. Body surface area (BSA) dosing (mg/m²) incorporates both height and weight, which can better account for metabolic factors. BSA dosing is often used for chemotherapy drugs and some medications for children because it correlates better with physiologic parameters like cardiac output and blood volume.
Why is renal function important for medication dosing?
Many medications are eliminated from the body through the kidneys. When kidney function is reduced, these drugs can accumulate to potentially toxic levels if doses aren't adjusted. Creatinine clearance provides an estimate of kidney function, allowing for appropriate dosage adjustments for patients with renal impairment. This is especially important for elderly patients and those with known kidney disease.
How do I convert between different units of measurement?
Common conversions include:
- Weight: 1 kg = 2.2 lb
- Height: 1 inch = 2.54 cm
- Creatinine: 1 mg/dL = 88.4 μmol/L
Our calculator automatically handles these conversions when you select different units.
What is the "Rule of 6" for medication calculations?
The Rule of 6 is a method used primarily in pediatric critical care to prepare continuous infusions. It involves adding 6 times the patient's weight (in kg) of a medication (in mg) to a solution to make a final volume of 100 mL. With this preparation, 1 mL/hr delivers 1 mcg/kg/min of the drug. This standardized approach simplifies calculations and reduces the risk of medication errors for drugs like dopamine and dobutamine.