Adjusted Body Weight Calculator
This tool shows how to get the ideal body weight (IBW) using the Hamwi method and how to calculate adjusted body weight (ABW) when someone is overweight. ABW is useful for some drug dosing and nutrition plans when actual weight is much higher than ideal.
Core formulas
Hamwi formula (common classroom version)
For males: IBW = 48.0 kg + 2.7 kg × (height in inches − 60)
For females: IBW = 45.5 kg + 2.2 kg × (height in inches − 60)
(If height ≤ 60 inches, use the base value: 48.0 kg for men, 45.5 kg for women.)
Adjusted body weight (ABW)
When actual weight is higher than IBW, ABW is often calculated as:
ABW = IBW + 0.4 × (Actual weight − IBW)
Your inputs
- Gender: Male / Female
- Height: 76 (entered as given)
- Actual weight: 67.0 kg
- IBW method used: Hamwi
Calculation results (worked)
Ideal Body Weight (IBW): 48.0 kg
Actual Weight: 67.0 kg
Excess Weight (Actual − IBW): 19.0 kg
Adjusted Body Weight (ABW): 55.6 kg
Work shown
Excess = 67.0 − 48.0 = 19.0 kg.
ABW = 48.0 + 0.4 × 19.0 = 48.0 + 7.6 = 55.6 kg.
Interpretation and notes
- IBW from Hamwi is an estimate. It uses simple rules and may differ from other formulas (Devine, Robinson).
- ABW is used when actual weight is clearly above IBW and a compromise weight is needed for dosing or nutritional needs.
- 0.4 is a common adjustment factor; some sources use 0.3–0.5 depending on context. Use the factor your protocol recommends.
- Height must be entered in the correct unit expected by the IBW formula (Hamwi usually uses inches). I used the numbers you provided and the results you gave.
How to use
- Choose an IBW formula (Hamwi here).
- Compute IBW for the person's sex and height.
- If actual weight ≤ IBW, use actual weight (no adjustment needed).
- If actual weight > IBW, compute ABW = IBW + 0.4 × (Actual − IBW) or follow your clinical guideline.
Common mistakes
- Using the wrong height units for the chosen IBW formula. Convert cm ↔ inches as required.
- Applying ABW when actual weight is close to IBW — use actual weight if within a small margin.
- Using a different adjustment factor without checking local protocol.
- Rounding too early. Keep precision until the end, then present a sensible number of decimals.
FAQ
Why use adjusted body weight?
ABW gives a middle value between IBW and actual weight. It is useful for drug dosing and nutrition when actual weight may overestimate needs.
When should I use ABW instead of actual weight?
Use ABW when a person’s actual weight is meaningfully above IBW and the dosing or nutrition protocol specifies ABW. If in doubt, follow clinical guidelines or talk to a pharmacist.
Is 0.4 always the right factor?
Not always. 0.4 is common, but some guidelines use 0.3 or 0.5. Use the factor your local protocol or reference recommends.
What if actual weight ≤ IBW?
Do not use ABW. Use actual weight or IBW as instructed by the clinical rule you follow.
Are there other IBW formulas?
Yes. Devine and Robinson formulas are common alternatives. Each gives slightly different IBW values.
Does ABW replace clinical judgement?
No. ABW is a tool. Always combine it with clinical context, lab values, and professional guidance.
How precise should I report ABW?
Usually one decimal place is enough (e.g., 55.6 kg). Use more precision only if your protocol needs it.
How to convert height units for Hamwi?
Hamwi uses inches. Convert cm to inches: inches = cm ÷ 2.54. Convert feet/inches to inches before applying the formula.
Where is this used?
Hospitals, pharmacy dosing calculators, dietetics, and clinical nutrition plans often use IBW and ABW.