Adjusted Weight Calculator
Calculate IBW (Devine formula), AdjBW for drug-dosing decisions in obesity, and pre-amputation weight estimates from body-segment fractions.
Calculation results
AdjBW is an educational estimate of dosing weight. The dosing weight used for a specific drug (IBW, AdjBW, or actual weight) is determined by the physician/pharmacist based on the drug’s properties and the patient’s condition.
Estimated results
Estimate based on average population fractions; individual proportions vary. For educational reference, not a substitute for clinical assessment.
Methodology
| Component | Formula |
|---|---|
| IBW Devine — men | 50 + 2.3 × (heightinches − 60) kg |
| IBW Devine — women | 45.5 + 2.3 × (heightinches − 60) kg |
| Adjusted body weight | IBW + 0.4 × (actual weight − IBW) |
| Estimasi pre-amputasi | current weight ÷ (1 − Σ segment fractions) |
Unit conversions: 1 inch = 2.54 cm; 1 kg = 2.2046226218 lb. The Devine formula is linear for all heights — below 60 inches it automatically subtracts 2.3 kg per inch.
Scope boundary
Frequently asked questions (FAQ)
What is adjusted body weight (AdjBW)?
Adjusted body weight (AdjBW) is a corrected body weight used as the dosing weight in patients with obesity. The formula: AdjBW = IBW + 0.4 × (actual weight − IBW), where IBW = ideal body weight (Devine formula). The 0.4 correction factor accounts for the fact that adipose tissue distributes some drugs, but not as much as lean tissue does.
What is the Devine formula for calculating IBW?
The Devine formula (1974): men IBW = 50 + 2.3 × (height in inches − 60); women IBW = 45.5 + 2.3 × (height in inches − 60), result in kg. For heights below 60 inches the formula stays linear: subtract 2.3 kg per inch below 60. Example: a 70-inch man -> IBW = 50 + 2.3 × 10 = 73 kg.
IBW vs AdjBW: what is the difference and when is each used?
IBW (ideal body weight) is a reference weight derived from height; AdjBW is IBW corrected toward actual weight with the 0.4 factor. In patients with obesity, some drugs are dosed on AdjBW, others on IBW or actual weight, depending on the drug’s properties. The dosing-weight decision belongs to the clinician or pharmacist — this calculator is only an educational tool for understanding the math.
What is the 0.4 correction factor in AdjBW?
The 0.4 factor is an empirical constant assuming that about 40% of the excess weight above IBW behaves like lean tissue for drug distribution. It is a consensus value widely used in the clinical pharmacy literature, not an individual measurement — for specific drugs clinicians may use a different factor or approach.
Can this calculator’s results be used to determine drug doses?
Not directly. This calculator is an educational tool. Actual drug doses must be determined by a physician or pharmacist who considers the drug type, kidney and liver function, age, patient condition, and applicable clinical guidelines. Do not change drug doses based on an online calculator without consulting a healthcare professional.
How do you estimate body weight for an amputation?
Current weight after amputation divided by (1 − total fraction of lost segments). Example: 80 kg with a one-sided lower-leg amputation (fraction 4.4%) -> estimated pre-amputation weight = 80 / (1 − 0.044) = 80 / 0.956 = 83.68 kg. For bilateral amputations, the fraction is doubled.
What is the weight fraction of each amputated body segment?
Standard fractions (one side): hand 0.7%, forearm 1.6%, whole arm 5%, lower leg 4.4%, thigh 10.1%, whole leg 16%. Bilateral amputation = fraction doubled. The whole arm already includes the hand and forearm; the whole leg already includes the thigh and lower leg — do not double-count.
Does AdjBW apply to children, pregnant women, or older adults?
The Devine formula was developed for adults and is not validated for children; pregnancy changes body composition so IBW/AdjBW do not apply; in older adults, reduced muscle mass means interpretation needs clinical caution. This calculator assumes a non-pregnant adult population.
Which units does this calculator support?
Height: centimeters (cm) or feet+inches (ft/in). Weight: kilograms (kg) or pounds (lb). All core calculations use kg and cm; unit conversions use 1 inch = 2.54 cm and 1 kg = 2.2046226218 lb.
How does this tool differ from a weight converter?
A weight converter (https://nrtechstudio.com/tools/weight-converter/) only converts weight units (e.g., kg to lb) — pure conversion with no clinical math. This tool computes adjusted body weight from the Devine formula and pre-amputation weight estimates from body-segment fractions. Different need, different tool: for unit conversion use the weight converter, for clinical calculations use this tool.
How accurate is the pre-amputation weight estimate?
This is an estimate based on average population fractions, not an individual measurement. Everyone’s segment proportions differ (muscle vs fat, dominant side). The result is useful as an educational reference and for screening, not as a substitute for clinical assessment or direct measurement.
Worked example: a 70-inch man weighing 120 kg, what is his AdjBW?
Step 1: IBW = 50 + 2.3 × (70 − 60) = 73 kg. Step 2: AdjBW = 73 + 0.4 × (120 − 73) = 73 + 18.8 = 91.8 kg. Difference vs actual weight: (91.8 − 120) / 120 = −23.5%. The calculator shows a step breakdown like this for every calculation.
Is the data I enter sent to a server?
No. This calculator is 100% client-side: all calculations run in your browser using JavaScript, with no network requests to any server. No height, weight, or medical data is sent or stored outside your device.
Where can I calculate BMI from actual weight?
For BMI (body mass index) using actual weight and height, use https://nrtechstudio.com/tools/bmi-calculator/. BMI and AdjBW answer different questions: BMI classifies weight status, AdjBW estimates dosing weight in obesity.
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