Adjusted Body Weight Calculator Formula

Understand the math behind the adjusted body weight calculator. Each variable explained with a worked example.

Use the Adjusted Body Weight Calculator

Formulas Used

Ideal Body Weight

ideal_weight = ibw

Adjusted Body Weight

adjusted_weight = ibw + 0.4 * (actual_weight_kg - ibw)

Percent Over IBW

pct_over_ibw = (actual_weight_kg - ibw) / ibw * 100

Variables

VariableDescriptionDefault
height_inchesHeight(inches)70
actual_weight_kgActual Body Weight(kg)110
gender_baseGender50
ibwDerived value= gender_base + 2.3 * max(height_inches - 60, 0)calculated

How It Works

Dosing Weight Calculations

Ideal Body Weight (Devine Formula)

Male: IBW = 50 + 2.3 x (height in inches - 60) Female: IBW = 45.5 + 2.3 x (height in inches - 60)

Adjusted Body Weight

AdjBW = IBW + 0.4 x (Actual Weight - IBW)

Adjusted body weight is used for drug dosing in obese patients (>20% above IBW) because many drugs do not distribute fully into adipose tissue.

Worked Example

A 70-inch tall male weighing 110 kg.

height_inches = 70actual_weight_kg = 110gender_base = 50
  1. 01IBW = 50 + 2.3 x (70 - 60) = 73 kg
  2. 02AdjBW = 73 + 0.4 x (110 - 73) = 73 + 14.8 = 87.8 kg
  3. 03Percent over IBW = (110 - 73) / 73 x 100 = 51%

Ready to run the numbers?

Open Adjusted Body Weight Calculator