There are some computer programs to calculate germination related traits such as Germin which have using problems. The aim of this work was to adjust Germin for calculating germination related traits. Seed aging effects on the seedling emergence was modeled using the optimized Germin. This study was conducted based on completely randomized design in a factorial combination of five seeds aging treatments (0, 48, 72, 96 and 144h accelerated aging periods) and 3 levels of environmental factors. Results indicated that Chapman–Richards function adequately described cumulative emergence in all aging treatments and three environmental conditions. Emergence percentage and rate were decreased by seed aging periods from 145 to 194oC day. Results showed that observed thermal time for emergence increased as accelerated ageing periods increased and drought stress resulted in increased thermal time. For example, thermal time increased to 240oC day in 144h accelerated aged seeds in severe drought. Results indicated that with increasing thermal time in optimum condition, thermal time would increase linearly in the drought stress. Optimized program could calculate germination related traits. Therefore, it is recommended to use the optimized Germin in seed science research.