A thermodynamic framework is established to calculate the solubility of inorganic salts in nonaqueous solvents. New solubility data of potassium iodide in selected organic solvents of acetone, ethanol, and 1-propanol are determined in the temperature range of 278-343 K. The experimental solubility is modeled by the methodology proposed in this work, and the solubility products of potassium iodide in organic solvents are estimated. Following this, the experimental mean activity coefficients are modeled with the electrolyte activity coefficient models of Pitzer, e-NRTL, e-Wilson equations, and their modified forms. Model parameters are optimized by fitting the experiment data. It turns out that the three-parameter e-Wilson equation presents the best correlation results with an overall average percentage relative deviation ARD of 1.36%. When the models are extrapolated to predict the low temperature solubility of potassium iodide in acetone down to 215 K, the three-parameter e-NRTL gives the most reliable predictions. A novel simple predictive mixing rule for the e-Wilson equation is proposed to estimate the solubility of potassium iodide in binary mixed solvents. The predictions are in good agreement with the experimental data of potassium iodide in water and ethanol over wide ranges of concentration and temperature.