This paper describes an analytical delay model for transistor sizing. Two primitives are selected to be mapped for computing gate delay. These primitives model the short-channel effect and body effect in deep submicron CMOS circuits. A mapping algorithm for arbitrary serial-parallel structures is adopted. The delay of complex gates using such mappings to primitives are found to be within 10% of SPICE for most of the gates. The delay model is incorporated into a transistor sizing algorithm based on TILOS. Also presented are the experimental results for several circuits from LGSynth91 benchmark suite.