Code shortening is commonly performed in practice but its analytical decoding performance is not well understood. In this letter, we present tight bounds for estimating the weight enumerator and hence BER (bit error rate) performance of linear shortened and shortened-extended block/product codes operating in AWGN and Rayleigh fading channels. The bounds are easy to use as they are expressed in terms of the original (unshortened) code properties, which are widely reported. Asymptotic coding loss expressions associated with code shortening are also derived.