This paper deals with disturbance attenuation capabilities of continuous linear time-invariant systems with respect to stochastic input disturbance with bounded 2 or power norm (for generality called N norm). A set of the input disturbances is bounded by the scalar parameter s which is determined by entropy integral and called σ-entropy. This set is connected with system bandwidth at low frequencies. S-entropy norm of the continuous linear system can be defined as a supremum ratio between N norms of the system’s output and input signals. It characterizes system gain of the stochastic input disturbance. In the paper a state-space solution to σ-entropy norm calculation is given.