Adjusted Body Weight Calculator

Health

The Adjusted Body Weight Calculator estimates the dosing weight used in clinical settings when a person's actual weight is well above their ideal body weight (IBW). It first finds IBW from height and sex using the Hamwi formula, then applies AdjBW = IBW + 0.4 × (actual weight − IBW). It is for educational reference, not medical advice.

Rates and fees change frequently. Always confirm the current figures with the official authority before relying on this result.

Formula

AdjBW = IBW + 0.4 × (Actual Weight − IBW); IBW(Hamwi) = 48.0/45.5 kg + 2.7/2.3 kg per inch over 5 ft (men/women)
  • Ideal body weight (IBW) is found with the Hamwi formula from height and sex.
  • Adjusted body weight adds 40% of the weight a person carries above their IBW: AdjBW = IBW + 0.4 × (actual − IBW).
  • It is mainly used for drug dosing in people whose actual weight is more than about 30% above IBW; below that, actual body weight is typically used.
  • This is an educational reference and not a substitute for clinical judgement.

Example Calculation

Inputs
  • Sex: male
  • Actual body weight (kg): 90
  • Height (cm): 170

A 170 cm man has IBW ≈ 65.6 kg. At 90 kg actual weight, AdjBW = 65.6 + 0.4 × (90 − 65.6) ≈ 75.4 kg.

Frequently asked questions

What is adjusted body weight?
It is a dosing weight between ideal and actual body weight, used clinically when a person weighs substantially more than their ideal body weight.
When is it used instead of actual weight?
Typically when actual weight exceeds ideal body weight by roughly 30% or more, for certain medications. Otherwise actual body weight is usually used.
How is ideal body weight calculated here?
With the Hamwi formula: 48.0 kg (men) or 45.5 kg (women) for the first 5 ft of height, plus 2.7 kg (men) or 2.3 kg (women) per inch above that.
Why the 0.4 factor?
It accounts for the fact that excess body mass is partly metabolically active tissue, so only a fraction of the weight above IBW is added.
Is this medical advice?
No. It is an educational estimate. Dosing decisions should always be made by a qualified clinician.