Ideal Body Weight Calculation for Adult Females
For adult females, ideal body weight (IBW) is calculated as 48.67 kg plus 1.65 kg for each inch of height above 5 feet (152.4 cm), or alternatively, height in centimeters divided by 105.
Primary Formulas for Female IBW
Modified Devine Formula (Most Widely Endorsed)
- IBW (kg) = 48.67 + 1.65 × (inches above 5 feet) 1, 2
- This formula is strongly recommended by the European Society of Cardiology for antithrombotic drug dosing and is derived from Metropolitan Life Insurance data 1, 2
- For example, a woman who is 5'6" (66 inches) tall: IBW = 48.67 + (1.65 × 6) = 58.57 kg 2
Simplified Height-Based Formula
- IBW (kg) = Height (cm) ÷ 105 1, 3
- Endorsed by anesthesiology guideline societies for rapid bedside calculations 1
- For a woman 165 cm tall: IBW = 165 ÷ 105 = 57.1 kg 1
Hamwi Method (Not Scientifically Validated)
- IBW (lb) = 100 lb for first 5 feet + 5 lb per additional inch 4, 1
- Approximately 45 kg for first 152.4 cm + 2.3 kg per additional 2.54 cm 1
- Caution: This method lacks scientific validation and should not be used for clinical dosing decisions 4, 1
When to Use Adjusted Body Weight Instead
Indications for Adjustment
- Use adjusted body weight (ABW) when actual weight is <95% or >115% of IBW 1
- For patients with BMI ≥30 kg/m², calculate ABW to avoid medication overdosing 1, 3
Adjusted Body Weight Formula
- ABW (kg) = IBW + 0.4 × (Actual Weight - IBW) 1, 3
- The 0.4 factor reflects that approximately 40% of excess adipose tissue is metabolically active 1
- Alternative factors exist for specific contexts: 0.33 for nutritional assessment (ESPEN), 0.25 for dialysis patients (KDOQI) 1
Clinical Context and Limitations
Important Caveats
- IBW formulas are derived from Metropolitan Life Insurance data and are not generalizable to chronic kidney disease populations 4, 1
- These equations were developed on healthy individuals and may not accurately reflect optimal weight for reducing morbidity and mortality in all populations 4
- For obese patients, using total body weight instead of IBW or ABW markedly increases risk of medication overdose, hypotension, and intraoperative awareness under anesthesia 1, 3
Special Population Considerations
- Hemodialysis patients: Use post-dialysis (edema-free) weight as the actual weight input 1
- Peritoneal dialysis patients: Use post-drainage weight after dialysate removal 1
- Patients with cardiac disease or age ≥70 years: IBW is still calculated the same way, but medication dosing should start lower and titrate gradually 1
Alternative Approach Using BMI
- Some clinicians prefer using BMI of 22 kg/m² to define ideal weight, as this is associated with lowest mortality 5, 6
- A universal equation: Weight (kg) = 22 × Height (m)² provides weights aligned with BMI 22 5, 7
- For women, this approach may be more accurate than traditional IBW formulas, which tend to underestimate at shorter heights and overestimate at taller heights 6