It is important to reduce the Optical Proximity Correction (OPC) runtime while maintaining a good result quality. In this paper, we obtain a better formula, which theoretically speeds up the widely used method, Optimal Coherent Approximations (OCA’s), by a factor of 2×. We speed up the OPC algorithm further by making it intensity based (IB-OPC), because it requires much less intensity simulations than the conventional Edge Placement Error (EPE) based OPC algorithms. In addition, the IB-OPC algorithm, which uses the efficiently computed sensitivity information, converges faster than the EPE based OPC. Our IBOPC experimental results show a runtime speedup of up to 15× with a comparable result quality as of the EPE based OPC.