Abstract Conventional methods for solving robot forward dynamics are characterized by high computational complexity. Recursive Newton-Euler algorithm (RNEA) is the most efficient computational method used for deriving a manipulator's dynamic equations of motion. In order to solve robot forward dynamics using RNEA in the most widely used Walker and Orin's method 1, it is necessary to execute RNEA n + 1 times, where n is the number of degrees-of-freedom (DoF). Herein, a simple and efficient method to solve forward dynamics using the modified RNEA (mRNEA) only once is presented. The proposed method is significantly more beneficial when used for robot simulations as it does not require calculating joint torques as inputs for forward dynamics unlike other methods. Further, an algorithm that calculates the joints’ accelerations based on forward dynamics while considering the actuators’ force/torque saturations and achieves a realistic simulation of robot movements is presented. The proposed mRNEA, its application in the presented forward dynamics algorithm, and the efficiency of the presented algorithms are demonstrated using a serial 6-DoF robot as an example.