Apparatus is disclosed for measuring the circumference of a limb of an individual, e.g., the individual's arm and/or calf. The apparatus uses one or more magnetic strips which surround the limb and contain magnetic coding of length information. Tension is applied to the magnetic strip by a tensioning assembly, which can be a pressure cuff or a stepping motor, and a magnetic read head reads the magnetic coding of length information from the strip. When used in a bioimpedance analysis procedure, the length information can be used to convert measured voltage differences into normalized bioimpedance values, e.g., resistivity values.