Schaefer et al developed an equation for estimating fat-free mass (FFM) in a child using bioelectrical impedance. The authors are from the University Children’s Hospital at Heidelberg and the Nuclear Research Centre at Karlsruhe.

Patient selection: German children from 3.9 to 19.3 years of age



(1) age in years

(2) height in cm

(3) resistance in ohms from bioelectric impedance


resistance index = RI =

= ((height in cm)^2) / (resitance in ohms)


fat free mass in kilograms =

= (0.65 * (resistance index)) + (0.68 * (age in years)) + 0.15

To read more or access our algorithms and calculators, please log in or register.