Droplet formation in microfluidics involves the flow of an immiscible liquid to form single droplets dispersed in a microfluidic channel. The control of the microfluidic droplet size produced in a microfluidic junction is far-reaching in several mechanical, biomedical and optical applications. This paper presents a numerical computation to study a droplet evolution in a T-junction microfluidic device. The normal flow velocity of the inlet is given for oil and water flows. The effect of inlet velocity on droplet size and droplet generation frequency is observed using COMSOL Multiphysics software. To observe the variation in droplet size and generation frequency, the inlet velocities for water and oil phases are varied from 30mm/s to 70mm/s and 80mm/s to 120mm/s, respectively. The numerical results show that the droplet volume decreases and the production frequency increases as the continuous phase inlet velocity is increased, consistent with conservation laws. The control of inlet velocities consequently manipulates the droplet size.