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Adjusted Body Weight Calculator

Enter sex, height and actual weight to get the ideal body weight (Devine), adjusted body weight, lean body weight, BMI and % of ideal weight, with the working. For pharmacists, doctors and nurses.

Sex

0.4 is usual; some protocols use 0.3 or 0.5

Ideal body weight (Devine)
75 kg
Adjusted body weight
85 kg
Lean body weight
69.5 kg
Actual weight vs IBW
133%
BMI
30.9
  • IBW = 50 + 2.3 × (70.87 in − 60) = 74.99 kg.
  • AjBW = IBW + 0.4 × (actual − IBW) = 74.99 + 0.4 × (100 − 74.99) = 85 kg.
  • LBW (Janmahasatian) = 9,270 × 100 ÷ (6,680 + 216 × 30.9) = 69.5 kg.

For pharmacists, doctors and nurses: body weight formulas only. Which weight a drug or protocol uses is set by its label and your local guidance; this tool doesn't give doses.

The formulas

  • Ideal body weight (Devine): 50 kg (men) or 45.5 kg (women) + 2.3 kg × (height in inches − 60)
  • Adjusted body weight: IBW + 0.4 × (actual weight − IBW); the factor can be changed
  • Lean body weight (Janmahasatian): 9,270 × weight ÷ (6,680 + 216 × BMI) for men, ÷ (8,780 + 244 × BMI) for women

Worked example

A woman 165 cm (64.96 in) tall weighing 90 kg: IBW = 45.5 + 2.3 × 4.96 = 56.9 kg; she weighs 158% of it, so AjBW = 56.9 + 0.4 × (90 − 56.9) = 70.1 kg. Her BMI is 33.1 and her lean body weight 49.5 kg.

Kidney function with these weights is on the creatinine clearance calculator.

Sources: Pai MP, Paloucek FP. The origin of the "ideal" body weight equations. Ann Pharmacother 2000;34:1066-9; Janmahasatian S et al. Quantification of lean bodyweight. Clin Pharmacokinet 2005;44:1051-65. Formulas only, no doses: verify against your drug's label and local protocol. Everything runs in your browser.

Frequently asked questions

How do I calculate adjusted body weight?

Work out the ideal body weight, then add 40% of the difference between actual and ideal weight: AjBW = IBW + 0.4 × (actual − IBW). For a man 180 cm tall weighing 100 kg, IBW is 75 kg, so AjBW = 75 + 0.4 × (100 − 75) = 85 kg.

What is the Devine ideal body weight formula?

50 kg for men or 45.5 kg for women, plus 2.3 kg for every inch of height over 5 feet. It was proposed in 1974 for gentamicin dosing and is still the most widely used IBW formula; it isn't well validated for people under 5 feet.

What is lean body weight?

An estimate of weight without fat, here by Janmahasatian and colleagues' 2005 formula: 9,270 × weight ÷ (6,680 + 216 × BMI) for men and ÷ (8,780 + 244 × BMI) for women. A woman of 165 cm and 90 kg has an LBW of about 49.5 kg.

When is adjusted body weight used instead of actual weight?

Usually when actual weight is well above ideal weight, for drugs that don't distribute much into fat. The threshold (often 120% or 130% of IBW) and the factor (0.4 is usual) depend on the drug and the local protocol, so this calculator shows all the weights and leaves the choice to you.

Does it work in pounds and inches?

Yes: switch height to inches and weight to pounds; the weights are shown in kilograms with pounds alongside.

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