Methods and apparatus for predicting/estimating the dry weight of an individual, e.g., a patient undergoing dialysis treatment, are provided. The techniques employ a bioimpedance measurement (303) on the individual's calf (101) to obtain information regarding the extracellular fluid volume of the calf. Using a measurement of the calf's circumference (309), a resistivity value is calculated, normalized by the individual's body mass index (BMI), and then offset by a reference value to obtain a new variable, DeltanRho, which is shown, by comparison with a "gold standard" (FIGS. 5-9), to be highly effective in predicting/estimating dry weight (FIGS. 10-13 and 15-16). The techniques are easy to use and provide accurate dry weight predictions/estimations without substantially adding to the complexity or cost of dialysis procedures. The techniques can also be used for individuals who are not renal patients, e.g., patients suffering from other diseases in which fluid overload can occur, athletes, fitness enthusiasts, and the like.