The purpose of this study is to estimate Reach 1-5+ using media models with only GRPs. The methodology, Logistic regression analysis used in this study, has never been used in the prior GRPs-Reach estimation studies. Study results show that logistic regression is a suitable method for estimating Reach for network & cable TV in Korea. For the application of logistic regression analysis, GRPs and Reach are converted into Ln(natural logarithm), Logit{Ln(odds)} forms respectively. The predicted Reach & Reach n+ are calculated by the algorithm with GRPs and Reach forms. Result also shows that the prediction error mean (MAE) for Reach 1+ is 3.5% for network TV and 3.66% for CATV. The method used in this study could help to reduce Network TV MAE compared to previous studies. Reach 2-5+ are also predicted with GRPs, Reach 1+, Reach 2+, …(Reach N-1)+ in this study. The MAEs for Reach 2-5+ are good enough compared to the estimation with BBD Model which is the most frequently used for predicting Reach n+. The R2 of all models were excellent over .90, and the prediction error(MAE) is less than 2.0%. In conclusion, this study shows a good sign for practical use to estimate Reach n+ without much efforts because it is possible to estimate Reach 1-5+ step by step with only GRPs in advance. It is expected to be possible to manage the budget of advertising costs efficiently with the models presented in this study.