Lukaski and Bolonchuk developed an equation for predicting an adult's extracellular water using personal information and bioelectrical impedance. This based on the corrected bromide space (CBS). The authors are from the US Department of Agriculture's Human Nutrition Research Center in Grand Forks, North Dakota.


Patient selection: middle-aged adults



(1) height in cm

(2) body weight in kilograms

(3) resistance in ohms measured by 4 electrodes (on hand and feet) at 50 kHz

(4) reactance in ohms (Xc)


extracellular water in liters =

= (0.052 * (weight in kg)) + (0.189 * (((height)^2) / (resistance in ohms))) - (0.0002 * (((height)^2) / (reactance in ohms))) + 1.03


intracellular water in liters=

= (total body water in liters) - (extracellular water in liters)



• The height squared divided by the resistance is called the impedance index.

• The formula for total body water is given above.

• The resistance and reactance are the lowest values measured at the 4 electrodes.



• R-squared was 0.884; the standard error of the estimate (SEE) was 1.01


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