Adjusted Body Weight Calculator
Adjusted body weight (AjBW) corrects ideal body weight for the extra metabolically active tissue carried in obesity. This calculator finds your ideal body weight from one of four clinical formulas, then reports adjusted and nutritional body weight, percent of ideal, BMI and body surface area in metric or imperial units.
Formula
Worked example
A 170 cm man weighing 90 kg has a Devine IBW of 50 + 2.3 x (66.9 - 60) = 65.9 kg. Adjusted body weight = 65.9 + 0.4 x (90 - 65.9) = 75.5 kg, nutritional body weight = 65.9 + 0.25 x 24.1 = 71.9 kg, and actual weight is 137% of ideal.
What is adjusted body weight?
Adjusted body weight (AjBW) is a clinical estimate used when a person carries substantial excess weight. Many drug doses and nutrition targets scale with lean, metabolically active tissue rather than total mass. Because adipose tissue contributes some, but not all, additional metabolic demand, AjBW adds a correction factor (commonly 0.4, or 40%) of the difference between actual and ideal body weight back onto the ideal figure. The result lands between ideal and actual weight, giving a more realistic dosing and energy basis for people with obesity than either extreme alone.
Adjusted vs nutritional body weight
Two related figures are used in practice. Adjusted body weight uses a 40% factor and is the usual choice for drug dosing in patients more than about 20% over ideal weight. Nutritional body weight uses a smaller 25% factor and is favoured in dietetics, often for patients more than about 30% over ideal, when estimating energy and protein needs. This calculator reports both at once so you can see how the choice of factor changes the result, and the advanced options let you switch which one is the headline figure.
Choosing an ideal body weight formula
Ideal body weight is the foundation of the adjustment, and several validated equations exist. The Devine formula (1974) is the most widely cited clinical default: 50 kg for men or 45.5 kg for women at 5 feet of height, plus 2.3 kg for every inch above that. Robinson (1983), Miller (1983) and Hamwi (1964) use different base weights and per-inch increments and can shift the ideal figure by a kilogram or two. Pick the one your institution uses; this tool defaults to Devine. All inputs are converted to metric internally and back to your chosen units for display, so metric and imperial give identical clinical results.
The extra context: %IBW, BMI and BSA
Alongside the weight figures the calculator reports percent of ideal weight, which is the trigger many protocols use to decide whether an adjustment is even needed. It also shows body mass index (BMI), weight in kilograms divided by height in metres squared, and body surface area (BSA) using the Mosteller formula, the square root of height in cm times weight in kg divided by 3600. BSA is widely used for chemotherapy dosing, while BMI gives a quick weight-status band. Together these turn a single number into a fuller clinical picture.
Ideal body weight formulas (per inch over 5 ft)
| Formula | Men base + per inch | Women base + per inch |
|---|---|---|
| Devine (1974) | 50 kg + 2.3 kg | 45.5 kg + 2.3 kg |
| Robinson (1983) | 52 kg + 1.9 kg | 49 kg + 1.7 kg |
| Miller (1983) | 56.2 kg + 1.41 kg | 53.1 kg + 1.36 kg |
| Hamwi (1964) | 48 kg + 2.7 kg | 45.5 kg + 2.2 kg |
Base weight at 5 feet plus a per-inch increment. Devine is the common clinical default.
Frequently asked questions
What is the difference between adjusted and nutritional body weight?
Both start from ideal body weight and add back part of the excess. Adjusted body weight uses a 40% factor and is the usual choice for drug dosing, while nutritional body weight uses a 25% factor and is common in dietetics for estimating energy and protein needs. This calculator shows both, and you can pick which is the headline result in the advanced options.
Why is the correction factor 0.4?
The 0.4 (40%) factor reflects the observation that excess adipose tissue still contributes some lean mass and metabolic activity, roughly 40% of the surplus behaves like the rest of the body for dosing purposes. Nutrition protocols often use 0.25 instead, so always follow your institution's guidance.
Which ideal body weight formula should I use?
Devine (1974) is the most widely cited clinical default and the one this tool starts with. Robinson, Miller and Hamwi are also validated and give slightly different values. Use whichever your hospital or clinic specifies; you can switch between all four in the advanced options.
What does percent of ideal weight tell me?
It is your actual weight divided by your ideal weight, times 100. Many protocols only apply an adjustment when this is above about 120% (drug dosing) or 130% (nutrition). Below those thresholds, adjusted and actual weight are close enough that the full actual weight is usually used.
Should I use adjusted body weight for everything?
No. Adjusted body weight is appropriate only for specific medications and nutrition calculations, and usually only when actual weight is well above ideal. Many drugs are dosed on actual, lean or ideal body weight. This tool gives general information, not medical advice, confirm the correct weight with a clinician.