In recent years, there are huge developments in Information and Communication Technology (ICT). ICT in present form has offered to interact with the computing system in users own language. But, there are several challenges to be addressed to achieve the full advantages of ICT. One of the biggest issue is standard text input mechanism. In practice, the text input mechanism is mainly realized through the virtual keyboard. A numbers of work have been proposed to design virtual keyboard with optimum layout. So that performance of text entry can be enhanced. Still there are demand of more improvement to make an efficient text entry mechanism. In this paper, a new concept of adaptation in virtual keyboard is proposed. Our objective is to develop a user friendly interface through adaptation of key size and centroid distance between keys. As a mean of adaptation, we provide several states (keyboard) on the basis of key size and center distance between keys. Upper and lower threshold values for a performance metric of a state are defined by evaluating the states using motor movement time and searching time. If one individual user performance is in between the range of upper and lower threshold values for the keyboard then no adaptation is required. Otherwise, the keyboard is adapted according an algorithm proposed in this paper. The proposed approach is experimented with real users and results substantiate the efficacy of the approach.