This paper introduces detail design of semi-custom CMOS Fast Fourier Transform (FFT) architecture for computing 16-point radix-4 FFT. FFT is one of the most widely used algorithms in digital signal processing. It is used in many signal processing and communication application as an important block for various multi-carrier systems such as for WLAN (Wireless local area network). This paper describes the design of an ASIC (Application Specific Integrated Circuit) CMOS FFT processor for 16-point radix-4 complex FFT computation, realized utilizing 0.18µm standard CMOS technology. Fixed point data format is preferred in comparison of floating point data format for a shorter dynamic range and reduced hardware utilization; thus, catering to the needs of portability. Furthermore, computations results at particular stage are rounded to avoid overflow issue and to be stored in register. The computation speed of the design is observed to be 50MHz after the synthesis process. Compared to traditional radix-4 algorithm the architecture proposed for 16-point FFT results in 1.73% of power saving and 5.5% of area reduction.