Calculator: Ideal body weight and adjusted body weight for adults

Input

Base weight for sex	Female (45.5)
	Male (50)
Height
Actual weight

Results

Important: Inputs must be complete to perform calculation.


Ideal body weight
Adjusted body weight

Decimal precision

Notes

Ideal body weight (IBW) and adjusted body weight (AdjBW, also known as “adjusted dosing weight”) may be used to determine weight-based dosing for some medications and in some estimates of kidney function. These equations are applicable to patients ≥5 feet (≥152.4 cm). For patients who weigh less than their IBW, actual (total) body weight is generally used.
Before use of these estimates, consult appropriate sources, including clinical drug reference(s) and institutional protocols; different equations are available and recommendations vary locally.
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.
IBW is sometimes used for calculating an initial weight-based dose of medications distributed primarily to non-adipose tissues, such as acyclovir, digoxin, rocuronium, and vecuronium. IBW may also be used for initial weight-based dosing for intravenous sedatives and opioids, with subsequent doses titrated to effect. For aminoglycosides, IBW may be used for determining the initial dose in patients who weigh from 1 to 1.25 times their IBW.^[2,3]
Calculating IBW is the first step in determining AdjBW.
AdjBW 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.
AdjBW may be useful for calculating an initial dose of aminoglycosides, daptomycin, lidocaine, and certain intravenous anesthetic agents in patients with a high body mass index (BMI).
This calculator reports an AdjBW of “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.
Separate calculators are available for estimating lean (non-adipose) body weight in adult male and female patients.
For specific recommendations, refer to the appropriate clinical topics and drug monographs included within UpToDate.
Equation parameters, such as Base weight for sex, have 2 or more discrete values that may be used in the calculation. The numbers in the parentheses, eg, (female = 45.5; male = 50), represent the values that will be used.

Equations used

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

AdjBW = IBW + (0.4 * [Actual_weight[kg] - IBW]

References

Devine BJ. Gentamicin therapy. Drug Intell Clin Pharm 1974; 8:650.
Hanley MJ, Abernethy DR, Greenblatt DJ. Effects of obesity on the pharmacokinetics of drugs in humans. Clin Pharmacokinet 2010; 49:71.
Erstad BL. Dosing of medications in morbidly obese patients in the intensive care unit setting. Intensive Care Med 2004; 30:18.
Shank BR, Zimmerman DE. Demystifying Drug Dosing in Obese Patients. American Society of Health-System Pharmacists 2016.

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All information contained in and produced by the EBMcalc system is provided for educational purposes only. This information should not be used for the diagnosis or treatment of any health problem or disease. THIS INFORMATION IS NOT INTENDED TO REPLACE CLINICAL JUDGMENT OR GUIDE INDIVIDUAL PATIENT CARE IN ANY MANNER. Click here for full notice and disclaimer.

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Calculator: Ideal body weight and adjusted body weight for adults