Energy saving is a critical issue in Wireless Sensor Networks as they have limited amount of energy and no rechargeable batteries. Clustering plays an effective role in utilization and saving of the limited energy resources of the deployed sensor nodes, where nodes are grouped into clusters and one node, called the cluster head is responsible for collecting data from other nodes, aggregates them and sends them to the BS, where data can be retrieved later. In multi-hop communication, the cluster head farthest away from the BS routes its data over several hops until they reach the BS. A network portioning problem arises when the nodes that are very close to the BS burdened with heavy relay traffic load and therefore die much faster than others. In this research we introduced a new unequal size clustering algorithm that balances the energy consumption among all clusters, where each cluster will have an optimal number of nodes, clusters that are close to the BS will have few number of nodes to be able to save energy for inter cluster communication compared to the ones that are far from the BS, that have large number of nodes. This optimal clustering algorithm helps to balance energy and prolong the life time of nodes. Simulation results show that our unequal clustering mechanism balances the energy consumption well among all nodes and it achieves an obvious improvement on the network lifetime.