Ideal Body Weight (IBW)

This tool calculates Ideal Body Weight and, where relevant, Adjusted Body Weight — then tells you directly which one (or actual body weight) to use for dosing this specific patient. See How Calculator Tools Work for the shared layout.

Inputs

• Height (cm — or feet/inches, converted automatically)
• Sex (male/female)
• Actual weight (kg — or lbs, converted automatically)

The formulas

Ideal Body Weight (Devine formula), using height in inches:

Male:   IBW = 50 + 2.3 × (height in inches − 60)
Female: IBW = 45.5 + 2.3 × (height in inches − 60)

This formula isn't valid below 5 feet (152 cm) — for shorter patients, the tool returns no IBW value and recommends using actual body weight instead.

Adjusted Body Weight, used only when a patient is significantly over their IBW:

AdjBW = IBW + 0.4 × (actual weight − IBW)

The dosing-weight recommendation

Rather than leaving you to interpret three numbers, the tool tells you directly which weight to dose from:

• IBW not calculable (height under 5 feet) → use actual body weight.
• Actual weight within 20% of IBW → use actual body weight.
• Actual weight more than 20% over IBW (i.e., obese by this measure) → use Adjusted Body Weight, specifically for renally-cleared drugs.

Reference

Devine BJ. Drug Intell Clin Pharm. 1974;8:650-655.