The past technique of calculating the flux of meteoroids capable of penetrating the skin of a spaceship is critically reviewed A new, more rigorous technique, compatible with any assumed meteoroidal flux, velocity distribution, and penetration equation, is derived using integral calculus Several values of a constant convenient for calculating the penetrating flux are calculated, assuming different values of the meteoroidal flux constants, different astronomically measured velocity distributions, and the Herrmann-Jones penetration equation The variation in the probability of penetration near the ballistic limit is shown to have negligible effect on calculated values of the penetrating flux The use of a normal, rather than a Poisson, distribution to calculate the probability of penetration is discussed