A combinatorial circuit with pre-calculation and having shorter delay is described. The combinatorial circuit uses information available from earlier input signals to pre-calculate intermediate signals, which are used to generate output signals when the last input signal arrives. The combinatorial circuit includes an input calculation block, at least one pre-calculation block, and an output calculation block coupled in series. The input calculation block receives some input signals and generates intermediate signals for the first pre-calculation block. The pre-calculation block(s) receive at least one earlier input signal and generate additional intermediate signals. The output calculation block receives the latest input signal and the intermediate signals from the last pre-calculation block and generates the output signals. The pre-calculation block(s) and the output calculation block may be implemented with simple circuits. In another aspect, a delta sigma (ΔΣ) modulator may use the combinatorial circuit with pre-calculation in order to improve operating speed.