Due to the increasing demand for network bandwidth, reliability, tolerability, scalability, and accuracy for transferring the data among several end to end entities. Several MPTCP (extension of regular TCP to hold multiple connections by a single TCP user to transfer the data simultaneously) algorithm have been proposed, but they sometimes fail to utilize the available bandwidth in an optimum way. So, in this paper, we propose a congestion control algorithm for MPTCP, named as Optimal Bandwidth Utilized algorithm (OBUA), in which the congestion window corresponding to a subflow shared by the number of regular TCP connection is increased maximum to its available bandwidth through bandwidth estimation mechanism, without harming the regular TCP connections that it is friendlier towards regular TCP. Here, we also propose a mechanism to estimate the available bandwidth of a flow and estimated bandwidth for the future load. Our proposed algorithm performs better than the existing algorithms for multipath TCP.