The multi-point method using more than four displacement sensors requires selections from non-unique filters deriving out-of-roundness from sensor outputs in the case of the conventional calculation technique using inverse filtering with frequency analyses. This paper analyzes propagations of sensor noises in the calculation process of out-of-roundness estimation, and shows that the calculation technique of multi-point method using pseudo-inverse matrix optimizes the calculation process and minimizes propagations of random noises occurring in sensor outputs without laborious calculations in search of the optimized filter.