Ideal Body Weight

Ideal body weight (IBW) was initially introduced by Devine in 1974 to allow estimation of drug clearances in obese patients; researchers have since shown that the metabolism of certain drugs relates more to IBW than total body weight. The term was based on the use of insurance data that demonstrated the relative mortality for males and females according to different height–weight combinations.

The most common estimation of IBW is by the Devine formula; other models exist and have been noted to give similar results. Other methods used in estimating the ideal body weight are body mass index and the Hamwi method. The IBW is not the perfect fat measurement as it does not show the fat or muscle percentage in one’s body. For example, athletes’ results show that they are overweight when they are actually very fit and healthy. Machines like the dual-energy X-ray absorptiometry (DXA) can accurately measure the percentage and weight of (fat, muscle, bone) in a body.

Formula

IBW
Estimated 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.

Examples

Example 1

Calculate the ideal body weight (IBW) of a man who is 64 inches tall and weighs 70 kilograms.  If this man is obese (> IBW + 30%), calculate the adjusted body weight.

To solve the example using the calculator, select the radio button for male. Next, enter the height (inches)  and weight (kilograms):

weight = 70 kg
height = 64 inches
IBW = 59.2

Or solve using formula:

IBW = 50 kg + 2.3 x each inch over 5 feet (60inches)
IBW = 50 kg + 2.3 x 4 inches
IBW = 50 kg + 9.2
IBW = 59.2 kg

The man’s actual weight is less than IBW + 30% so it is not necessary to calculate the adjusted body weight (ABW).

Example 2

Calculate the ideal body weight (IBW) of a woman who is 64 inches tall and weighs 80 kilograms.  If this woman is obese (> IBW + 30%), calculate the adjusted body weight.

To solve the example using the calculator, select the radio button for female. Next, enter the height (inches)  and weight (kilograms):

weight = 80 kg
height = 64 inches
IBW = 54.7

Or solve using formula:

IBW = 45.5 kg + 2.3 x each inch over 5 feet (60inches)
IBW = 45.5 kg + 2.3 x 4 inches
IBW = 45.5 kg + 9.2
IBW = 54.7 kg

The woman’s actual weight is greater than the IBW + 30%, so calculate the ABW:

ABW = 54.7 kg + 0.4( 80kg – 54.7 kg)
ABW = 54.7 kg + 0.4( 25.3 kg )
ABW = 54.7 kg + 10.1kg
ABW = 64.8 kg

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