Two methods for post-synthesis circuit optimization are disclosed. In both methods, the underlying variability in process parameters is captured through a robust linear program. The robust linear program is then reformulated as a second order conic program that possesses special structural properties to allow for a computationally efficient solution by using interior point optimization methods. The first method treats gate delays as uncertain quantities and obtains the optimal sizes for gates in a circuit under a probabilistically specified circuit timing target. The second method optimizes total circuit power by using a combination of dual threshold voltage assignment and gate sizing. Both circuit power and timing are treated probabilistically.