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Calculator: Ideal body weight and adjusted body weight for adults

Calculator: Ideal body weight and adjusted body weight for adults

Base weight for sex Female (45.5)

Male (50)
Actual weight  

Important: Inputs must be complete to perform calculation.

Ideal body weight  
Adjusted body weight  
Decimal precision  


  • Ideal body weight (IBW) is estimated by the following equations:[1] Males: IBW (kg) = 50 kg + 2.3 kg for each inch over 5 feet. Females: IBW (kg) = 45.5 kg + 2.3 kg for each inch over 5 feet.
  • Calculating IBW is the first step in determining an "adjusted body weight" used for dosing of some medications in patients who are obese (see below).
  • IBW is sometimes used when estimating an initial dose of medications distributed primarily to non-adipose tissues, such as acyclovir, digoxin, rocuronium, and vecuronium. IBW may also be used for initial dosing for intravenous sedatives and opioids, with subsequent doses titrated to effect. For aminoglycosides, IBW can be used for determining the initial dose in patients who are 1 to 1.25 times their IBW.[2,3]
  • Adjusted body weight (AdjBW), also known as "adjusted dosing weight," is calculated using the formula:[3] AdjBW = IBW + (0.4 * [Actual weight - IBW]).
  • AdjBW is a calculated weight that accounts for the incomplete distribution of certain drugs to non-lean body tissues in obesity.
  • This calculator reports N/A for patients whose weight is >IBW but <120% of IBW, since the appropriate adjustment factor for patients in this weight range is unclear.
  • AdjBW may be useful for estimating initial doses of aminoglycosides, lidocaine, and certain intravenous anesthetic agents in patients who are obese.
  • Separate calculators are available for estimating lean (non-adipose) body weight in adult males and lean body weight in females.
  • For specific recommendations, refer to the appropriate clinical topics and drug monographs included within UpToDate.

Equations used
Ideal_body_weight[kg] = Base_weight_for_sex + (2.3 * (Height[in] - 60))


Equation parameters, such as Base weight for sex, have two or more discrete values that may be used in the calculation. The numbers in the parentheses, eg, (45.5), represent the values that will be used.

  1. Devine BJ. Gentamicin therapy. Drug Intell Clin Pharm 1974; 8:650.
  2. Hanley MJ, Abernethy DR, Greenblatt DJ. Effects of obesity on the pharmacokinetics of drugs in humans. Clin Pharmacokinet 2010; 49:71.
  3. Erstad BL. Dosing of medications in morbidly obese patients in the intensive care unit setting. Intensive Care Med 2004; 30:18.
  4. Shank BR, Zimmerman DE. Demystifying Drug Dosing in Obese Patients. American Society of Health-System Pharmacists, Bethesda, MD 2016.
Only digits 0 to 9 and a single decimal point (".") are acceptable as numeric inputs. Attempted input of other characters into a numeric field may lead to an incorrect result.

Information on this page may not appear correctly if printed.

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