Objectives: This study compares effective dose determination of four large field of view CBCT units (NewTom-3G, Galileos Comfort Plus, CS-9300, iCat-FLX,) using a Monte Carlo software analysis method (PCXMC) and dosimetry using anthropomorphic phantoms. Methods: Previous research provided phantom effective dose comparisons. Field-of-view and phantom positioning were duplicated in the software. Software and phantom dosimetry values were compared. Descriptive statistics, chi-square, and logistic regression, were used to analyze the data. The null-hypothesis that there is no statistically significant difference between the dosimetry values of the anthropomorphic phantom and the calculated values of the PCXMC software was tested. Results: PCXMC simulated scans produced dose values within 20% of the phantom dosimetry 48-58% of the time. Conclusions: While the software calculations are simpler to perform than phantom dosimetry, imprecise calculated results make this program less effective for CBCT dosimetry in dentistry.