Ideal Body Weight & Adjusted Body Weight
Ideal body weight (IBW) and adjusted body weight are frequently used clinically to adjust drug dosing, help estimate renal function and the pharmacokinetics in morbidly obese patients. The most common IBW equation used is the Devine formula.
Select option for calculating the IBW for patients under 60 inches :
(default option - BMI method) - ignore for all other patients.
[See reference section] Intuitive Method
Ideal body weight
Estimate Ideal body weight in (kg)
Males: IBW = 50 kg + 2.3 kg for each inch over 5 feet.
Females: IBW = 45.5 kg + 2.3 kg for each inch over 5 feet.
Devine BJ. Gentamicin therapy. DICP. 1974; 8:650–5.
Adjusted body weight
AjBW = adjusted body weight:
AjBW = IBW + 0.4( ABW - IBW)
1) Bauer LA. Applied clinical pharmacokinetics. New York: McGraw Hill,
Medical Publishing Division; 2001:93-179.
2) Winter, M.E., 2004. Basic pharmacokinetics. London: Lippincott
Williams and Williams.
Aminoglycosides /Vancomycin Empiric Dosing
Dosing By Levels
Background info for height less than 60 inches
If the actual body
weight is less than any of the calculation methods, the actual body
weight will be used.
Discussion of the various methods: The
output of this section is based on research I had completed ~20 years
ago on this subject. A quick review of the recent literature has
not changed or added any new methods for estimating an ideal body weight
for patients less than 60 inches tall. Note: naming convention is
based on my earlier work...
1] Intuitive Method:
Reference: Murdaugh LB. Competence Assessment Tools for
Health-System Pharmacies. 5th ed. Bethesda, MD: ASHP; 2015. [Chap:29 Medication
dosing in Patients with Renal Dysfunction]
IBW (Male) = 50kg - 2.3kg for each inch below 60 inches
IBW (Female) = 45.5kg - 2.3kg for each inch below 60 inches
Comments: For patients just a few inches below 60
inches, the result is reasonable, however, 2.3 kg/inch is excessive when
used for shorter heights. At 38 inches for a male, and 40 inches
for a female, the IBW is ZERO. This provides support for the
next method below.
2] Baseline Method:
The baseline method starts with the initial ideal body weight baseline
values e.g. 60 inch male patient - 50kg and 60 inch female patient -
45.5kg. Male patient: 50kg /60 inches = 0.833 kg/inch.
Female patient = 45.5kg/60 inches = 0.758 kg/inch. Therefore
a male patient - 55 inches: IBW = 50kg - (0.833 x 5) = 45.8kg versus the
first method = 50kg - (2.3 x 5) = 38.5 kg.
[Reference: reasonable assumption based on the standard ideal body weight
equations and the baseline weights established for a height of 60 inches. Also review: Murphy JE. Introduction. In: Murphy JE, ed. Clinical Pharmacokinetics, 5th ed. Bethesda, MD: American Society of Health-System Pharmacists, 2011:xxxiv.
- Note: for patients who are less than 60 inches tall, the weight should be decreased more conservatively than 2.3kg/inch.]
3] BMI method:
Wiggins, K. L. (2004). Renal care: Resources and practical applications.
Chicago: American Dietetic Association. pg 12.
Barash, P. G., Cullen, B. F., & Stoelting, R. K. (1989). Clinical anesthesia.
Philadelphia: Lippincott. chap:47:1231
Remember that BMI = weight(kg)/height 2 (meters squared).
Next, we will establish an 'ideal' BMI based on values in the standard
IBW equations: Male: 60 inches - 50kg - BMI= 21.53. Female:
60 inches - 45.5kg - BMI= 19.59. We can then use this association
to generate an equivalent ideal weight based on this standardized BMI
and the height of the patient. Using the example above (55 inch
IBW = 21.53 (BMI value above) x (55 x 0.0254) 2 =
Background info: the body mass index quantifies the amount of tissue mass at a
particular height (units: kg/m 2). Example: the following
patients all have a BMI ~ 21: 130 lbs - 5'6", 163 lbs - 6'2",
107 lbs - 5'.
4] Hume method:
LBW (Males) = (0.3281 x Weight in kg) + (0.33939 x Height in cm) -
LBW (Females) = (0.29569 x Weight in kg) + (0.41813 x Height in cm) -
Using the example above: (55 inch male patient): IBW=
Reference: Hume R. Prediction of lean body mass from height and
weight. J Clin Path(1966), 19, 389.
Estimated 'Calorie' Calculators
Estimation of total calories needed. MOST widely used equation for calculating basal metabolic rate and total calories.
Revised Harris-Benedict Equation:The original Harris Benedict equation was revised in 1984. This updated equation can be used to calculate the basal metabolic rate and total calories.
RESTING Metabolic Rate (RMR)
Resting Metabolic Rate Calc - This equation can be used to calculate the RESTING metabolic rate and total calories. Mifflin-St Jeor equation.
Schofield equation (BMR)
This equation was part of the previous government guidelines to formulate RDA's and can be used to calculate the basal metabolic rate and total calories needed.
Institute of Medicine Equation- LATEST EQUATION:
IOM Equation-Estimated Energy Requirement (EER) Estimation of total calories needed. This equation is behind the 2005 Dietary Guidelines for Americans and the new food pyramid, MyPyramid.