The omitting of small sectioned particles of secondary phase particles on an intersected plane of a specimen has been simulated. Characteristics such as the mean value, standard deviation, skewness, and kurtosis of a three-dimensional size distribution (3DSD), the volume fraction, and the number of particles per unit volume for the secondary phase particles are estimated from the overlooked two-dimensional size distribution (2DSD). The monodispersed system as well as the exponential, the Rayleigh, the lognormal, and the pseudonormal distributions are used as a probability density function of the 3DSD for the discrete 2DSD model. As a result, an extrapolation method is applicable to estimate the expedient values for the mean value and the number of particles per unit volume of particles, even if oversight of small sectioned particles occurs. The effect of omitting the small sectioned particles on the estimated volume fraction is found to be negligible.