We present a novel methodology to extract model parameters from measured S-parameters for silicon on-chip center-tapped symmetric spiral inductors. The double-pi equivalent circuit topology is employed in which conductor skin effect is considered. The automated extraction procedure based on modified differential evolution is demonstrated to be efficient and effective. To verify the accuracy of the new methodology, 17 center-taped symmetric inductors were fabricated and the equivalent circuit parameters were extracted from two-port S-parameters measurements over the frequency range of 0.3-8.5 GHz. The excellent accuracy of the results demonstrates the flexibility of the modeling methodology. The new methodology should be useful in the design of RF ICs and mixed signal ICs. (C) 2008 Elsevier Ltd. All rights reserved.