Ideal Body Weight Calculator
Determine your Ideal Body Weight (IBW) based on the clinically accepted Devine formula.
IBW Calculator
Calculate your Ideal Body Weight
Enter values to calculate...
Devine Formula Base
Base for 5 feet. Add 2.3 kg per inch over.
Base for 5 feet. Add 2.3 kg per inch over.
Use Adjusted Body Weight for dosing if actual weight exceeds 120% of IBW.
The Concept of Ideal Body Weight (IBW)
Ideal Body Weight (IBW) is a concept originally introduced by life insurance companies to determine the correlation between weight and mortality. In clinical practice today, IBW is primarily used for pharmacokinetic dosing calculations. Many medications, particularly those that are hydrophilic (water-soluble) like aminoglycosides, do not distribute well into fat tissue. Therefore, dosing based on actual body weight in obese patients could result in overdosing and toxicity.
The Devine Formula
The Devine formula (1974) is the most universally accepted equation for calculating IBW in medical settings. It is defined as:
- Male: 50 kg + 2.3 kg for each inch over 5 feet.
- Female: 45.5 kg + 2.3 kg for each inch over 5 feet.
Adjusted Body Weight (ABW)
If a patient's actual body weight is significantly greater than their ideal body weight (typically defined as >20% above IBW), clinicians often use the Adjusted Body Weight (ABW) for dosing certain drugs. The ABW accounts for the partial distribution of hydrophilic drugs into excess adipose tissue.
ABW = IBW + 0.4 × (Actual Weight − IBW)
This ensures that the patient receives an effective dose without reaching toxic levels.
Frequently Asked Questions
Why is the Devine formula used instead of others?
The Devine formula became widely adopted due to its simplicity and its integration into the Cockcroft-Gault equation for estimating creatinine clearance.
Is IBW my "healthy" weight goal?
Not necessarily. IBW is a strict clinical tool meant for drug dosing. For setting personal health and fitness goals, a healthy BMI range or body fat percentage is much more appropriate.
What if I am shorter than 5 feet?
The original Devine formula technically doesn't account for individuals under 5 feet (60 inches). Clinicians often subtract 2.3 kg for every inch below 5 feet, or use alternative formulas.
Why do males and females have different formulas?
Males generally have a higher percentage of lean muscle mass and bone density compared to females of the same height, which is reflected in the higher baseline weight in the formula.
When is Adjusted Body Weight used?
ABW is typically used when the patient's actual weight is 20-30% greater than their IBW, particularly when dosing medications with a narrow therapeutic index.
Medical Disclaimer: This calculator is for informational and educational purposes only. It is not intended as a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider. Read full disclaimer →