In this paper, we propose a novel signal to noise ratio algorithm based on the moments of the received signal. The novel algorithm has been designed for multi band orthogonal frequency division multiplexing (MB-OFDM) communication systems in ultra wide band channels. The proposed algorithm is a switched estimator that uses two equation models, one is for large SNR scale and the other for low SNR scale. The proposed model can be used for SNR estimation in adaptive modulation and channel estimation and link quality control in MB OFDM systems. This algorithm can be implemented in receivers with simple structures. The performance of the proposed SNR estimation algorithm and its comparison with other SNR estimators was achieved through simulations.