What adjusted body weight is for
Adjusted body weight (AdjBW) is a weight figure that sits between a person's ideal body weight and their actual weight. It exists because some quantities the body handles, such as certain drug distributions and energy or protein estimates, do not scale fully with excess weight, since fat tissue is less metabolically active than lean tissue. Using actual weight can overestimate the need and using ideal weight can underestimate it, so clinicians and dietitians often use a value in between.
This calculator computes ideal body weight from height and sex using the Devine formula, then applies the standard 0.4 adjustment factor to your actual weight. It is meant for information and education. Where a medication dose or nutrition plan is involved, the choice of weight, the correction factor and the resulting numbers belong to a qualified clinician, because different protocols use different factors and thresholds.
How it is calculated
Height in centimeters is converted to inches, and the Devine ideal body weight is computed, then the adjusted weight follows:
- Inches = height in cm ÷ 2.54.
- IBW (male) = 50 kg + 2.3 kg × (inches over 60); IBW (female) = 45.5 kg + 2.3 kg × (inches over 60). Heights at or under 60 inches use the base value.
- AdjBW = IBW + 0.4 × (actual weight − IBW), in kg.
- Actual as % of IBW = actual ÷ IBW × 100, and excess = actual − IBW.
- The 0.4 factor is a common convention; some references use values from 0.25 to 0.5 depending on the purpose.
Worked example
A man is 180 cm tall and weighs 100 kg. His height is 180 / 2.54 = 70.87 inches, which is 10.87 inches over 60. His IBW is 50 + 2.3 × 10.87 = 74.99 kg.
The excess over ideal weight is 100 − 74.99 = 25.01 kg. The adjusted weight is 74.99 + 0.4 × 25.01 ≈ 84.995 kg, which the calculator rounds to 85.00 kg. His actual weight is 100 / 74.99 = 133.3% of ideal. Those are the values the calculator shows for these inputs.
Common mistakes and how to interpret the result
- Using it when actual weight is below ideal. The adjustment is designed for people above their ideal weight. If actual weight is lower, the formula pulls the result upward, which is usually not what a protocol intends.
- Confusing it with BMI or healthy weight. Adjusted weight is a calculation weight for dosing and estimates, not a target or a health verdict.
- Entering pounds or inches. Height must be in centimeters and weight in kilograms. Convert first: 1 in = 2.54 cm and 1 lb = 0.4536 kg.
- Assuming one formula fits everyone. The Devine formula was developed for adults, ignores build and muscle mass, and may be inappropriate for children, very short or very muscular people.
Frequently Asked Questions
Why use 0.4 as the correction factor?
Is adjusted body weight the same as ideal body weight?
Can I use this to decide a medication dose?
Which ideal body weight formula does it use?
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