Mobile Ad hoc network - MANET is expected to play an important role in the future mobile communication. But multi hops data communication in MANET suffers severe low speed due to the dynamic nature of MANET and the competition for shared wireless resources between mobile nodes. To tackle this problem, efficient bandwidth estimation plays an important role. In this paper a new and efficient solution for available bandwidth estimation on MANET is proposed. In this solution, the destination node will send the probe packets to the source node so that the source node could estimate the available bandwidth between them. Doing so will reduce the number of probe packets to half. A new formula for available bandwidth estimation of 802.11 ad hoc network is also presented. The simulation results show that the proposed solution could estimate the available bandwidth very efficiently and accurately. It also shows that when the proposed solution is applied to the load balancing in MANET, connection's throughput is increased significantly, in both cases of using proactive and reactive routing protocol.