Ideal Body Weight (IBW) & Adjusted Body Weight (ABW) Calculator — Devine Formula
Calculate estimated ideal body weight (IBW) and adjusted body weight (ABW) using Devine, Robinson, Miller, and Hamwi formulas for mechanical ventilation tidal volume setting and drug dosing.
Ideal Body Weight Calculator
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This calculator is for informational and educational purposes. Results should be interpreted with clinical judgment and local guidelines.
What is Ideal Body Weight (IBW)?
Ideal Body Weight (IBW) is an estimated body mass calculated from height and biological sex, representing the baseline weight of maximum life expectancy based on historical insurance actuarial tables. The Devine formula (1974), originally developed for drug clearance calculations (such as the Cockcroft-Gault equation for creatinine clearance), is now the clinical standard used in critical care medicine. In mechanical ventilation, lung volumes depend on height and biological sex—NOT actual total body weight. The ARDSNet lung-protective ventilation protocol mandates calculating tidal volume (6 mL/kg of IBW) to prevent ventilator-induced lung injury (VILI) and volutrauma.
Devine IBW (Men) = 50 kg + 2.3 kg for every inch over 5 feet. Devine IBW (Women) = 45.5 kg + 2.3 kg for every inch over 5 feet. Adjusted Body Weight (ABW) = IBW + 0.4 × (Actual Weight − IBW).
When to Use the IBW Calculator
- Mechanical ventilation: Calculating lung-protective tidal volumes (4–8 mL/kg IBW) in ARDS and ICU patients.
- Drug dosage adjustments in obesity for hydrophilic drugs (Aminoglycosides, Acyclovir) using Adjusted Body Weight.
- Creatinine clearance estimation (Cockcroft-Gault formula uses IBW).
Devine & Alternative IBW Formulas
Devine Formula (Men)
IBW (kg) = 50 + 2.3 × (Height in inches − 60)
Man 5 ft 10 in (70 inches) → IBW = 50 + 2.3 × 10 = 73.0 kg
Devine Formula (Women)
IBW (kg) = 45.5 + 2.3 × (Height in inches − 60)
Woman 5 ft 4 in (64 inches) → IBW = 45.5 + 2.3 × 4 = 54.7 kg
Adjusted Body Weight (ABW)
ABW (kg) = IBW + 0.4 × (Actual Weight − IBW)
IBW = 60 kg, Actual Weight = 100 kg → ABW = 60 + 0.4 × 40 = 76.0 kg
Variables
Height (cm (or inches))
Total standing height. 1 inch = 2.54 cm.
Sex (Male / Female)
Biological sex at birth.
Actual Weight (kg)
Measured patient weight (used for ABW calculation).
For height < 5 feet (60 inches), some variants subtract 2.3 kg per inch below 60 inches.
Ventilator Tidal Volume Settings by IBW (ARDSNet)
Target tidal volume setting for mechanical ventilation based on IBW.
| Range | Classification | Health Risk |
|---|---|---|
| 4 mL/kg IBW | Lower ARDS Limit | Severe ARDS / high plateau pressure (> 30 cmH₂O). |
| 6 mL/kg IBW | Standard ARDSNet Target | Gold standard lung-protective target for ARDS / respiratory failure. |
| 8 mL/kg IBW | Upper Non-ARDS Target | Normal lungs without acute lung injury. |
Never set tidal volumes based on actual weight in obese patients; doing so causes severe lung barotrauma/volutrauma.
Limitations & Clinical Warnings
IBW formulas are valid for adults ≥ 5 feet (60 inches) tall.
Does not apply to pregnant women, amputees, or athletic individuals with extreme muscle mass.
Medical Disclaimer
Always use IBW for ventilator tidal volume calculations to prevent ventilator-induced lung injury (VILI).
References & Citations
- Devine BJ. “Gentamicin therapy”. Drug Intelligence & Clinical Pharmacy. 1974. 8: 650–655. DICP: 8:650–655
- ARDS Definition Task Force. “Acute respiratory distress syndrome: the Berlin Definition”. JAMA. 2012. 307(23): 2526–2533. PMID: 22797452
Medically Reviewed
Reviewed by CliniqWise Clinical Advisory Board — Critical Care Panel · Last updated: 2026-08-27 · Next review: 2027-02-27
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