This research developed a new approximation formula for the prediction of downwind location from stack source which found the maximum ground level concentration of air pollution (x_max) based on Gaussian Model using linear regression to obtain the relationship between the x_max and stack height (H) for each atmospheric stability class and each environmental condition. The estimated and actual x_max were summarized. The errors were in the range of -1.13 to 0.88% for the stack height between 10 – 250 m which has a better accuracy than the classical method of approximation.