Intersections are playing an important role in the traffic network. as they are the greatest congested areas, which most of the delay, accidents, oil consumption, and noises occurring in intersections. with a smooth traffic flow can avoid these issues. It is a need to implement the roundabouts in the intersections as will decrease the conflict point. there is no procedure to analyze the capacity of rotary for Afghanistan traffic scenario. The data have been collected from 8 rotaries from different regions of Herat city of Afghanistan, which 5 rotaries used for development and 3 rotaries used for validation of the developed model. For the development of theoretical capacity model, the driver behavior is one of the main components which impact the entry capacity. Critical gap and follow-time are the gap acceptance parameters for driver behavior. One of the most important factor in the capacity modeling of the rotary intersectionis critical gap. Different methods are using for estimation of critical gap namely: Raff graphical method, maximum likelihood method, and Equilibrium of probabilities method. Finally, by utilizing the gap acceptance parameters an equation based on multi-regression analysis have been developed which is computable with site data and other existing capacity models. The model compared with both highway capacity manual (HCM 2010) and Germany capacity model, as the result shows both models underestimate/overestimate the entry capacity of roundabout.