Gears are one of the most important machine elements in the industry. They are using many areas such as; automotive, energy, aviation, etc. Gears are exposed to higher loads day by day due to the increase in power and speed on the machines. Therefore, the stress values which are occur on the gear root is also increase. These stresses cause to damage on the teeth root. Thus the stress values have to be decrease to design optimum gear body. In this study, the effects of root radius on the gear bending stress are evaluated by using finite element method. At first, gears with standard root radius is investigated both DIN 3990 and finite element method. After the validation of finite element model, the root radius of the gear is taken as parameter. Gears with different root radiuses are analyzed by using finite element method. It is seen that with the increasement of gear tooth radiuses, the root stress is considerably decreased. With increasement of root radiuses the maximum principal stress reduced nearly 20%.