Adjusted Body Weight Calculator
Calculate Adjusted Body Weight (ABW) and Ideal Body Weight (IBW) using Devine, Robinson, Miller, and Hamwi formulas
Your Details
Quick examples
Reference estimate only — not medical advice. Dosing and clinical decisions must be made by a qualified healthcare professional.
Calculation Results
Interpretation
IBW & ABW by Formula
| Formula | IBW | ABW |
|---|
How we calculated this
IBW & ABW by Formula
What if?
Each row recalculates with your current inputs. Tap a row to apply it.
Compare two plans
Enter height and weight to calculate ABW
Fill in gender, height and actual weight above
Authoritative sources and references
The official standards, guidelines, and research behind this calculator's methodology.
Adjusted Body Weight Calculator FAQ
What is adjusted body weight used for?
ABW estimates a dosing or nutritional weight when actual body weight is well above ideal weight. It assumes only about 20% of the excess weight is metabolically active lean tissue — hence the 0.4 factor. It is commonly referenced for certain medication doses and nutrition assessments.
Why do the four IBW formulas differ?
Devine, Robinson, Miller and Hamwi were derived from different population data and purposes, so each gives a slightly different ideal weight. Devine is the most widely cited in clinical pharmacology. The comparison table shows all four side by side.
Which weight should be used — actual, ideal, or adjusted?
As a general convention: actual weight when below or near IBW, adjusted weight when well above IBW. The interpretation card shows where you fall. This is a reference convention only — the choice for a specific medication or nutrition plan belongs to your clinician.
How is adjusted body weight calculated?
The standard formula is ABW = IBW + 0.4 × (actual body weight − IBW), where IBW is ideal body weight from the Devine formula. The 0.4 factor reflects that adipose tissue is roughly 30% metabolically active lean mass, so full actual weight overcorrects and pure IBW undercorrects for patients with obesity.
When does adjusted body weight matter for medication dosing?
ABW is the standard dosing weight for weight-sensitive drugs such as aminoglycoside antibiotics (gentamicin, tobramycin) and theophylline. Using actual weight in patients with obesity can cause overdosing, while ideal body weight alone can cause underdosing — ABW sits deliberately between the two.
Does adjusted body weight apply to children?
No. Pediatric dosing is normally computed in mg per kg of actual body weight, and the adult IBW formulas and the 0.4 correction factor were never validated for children. For pediatric questions, follow the prescriber's instructions.
Accurate health and fitness calculators for BMI, ideal weight, and wellness tracking