Abstract: A method for real-time determination of water-filled porosity of a formation using dielectric measurement data, whereby the refractive index of a non-water component of the formation and the downhole temperature are acquired, along with the dielectric constant of the formation. Using these values, the water salinity of the formation is calculated. Calculation of the water salinity involves the use of a complex nonlinear equation having multiple solutions. A theorem is applied to the nonlinear equation which produces a single proper solution. Once the water salinity is calculated, it is then used to calculate the water-filled porosity of the formation.