Ideal / Adjusted Body Weight Calculation Ideal body weight calculation is to check the appropriate weight for height for an individual inorder to prevent any health risks. The calcualtion in based on Body Mass Index (BMI). Formulas Used: IBW (kgs) = 22 x (height in meters)2 ABW = IBW + 0.4( actual weight - IBW ) In obese patients, where actual body weight is >30% over calculated IBW, an Adjusted Body Weight (ABW) is often recommended for drug dosing. Free online Medical Calculators.