Preoperative breast volume estimation is very important for the success of the breast surgery. In this study four different breast volume determination methods were compared. The end-point of this prospective study was to evaluate the concordance between different modalities of breast volume assessment (MRI, BREAST-V, mastectomy specimen weight, conversion from weight to volume of mastectomy specimen) and the breast prosthetic volume implanted. The study enrolled 64 patients between 2017 and 2019, who had all been treated by the same surgeons for monolateral nipple-areola complex-sparing mastectomy and implant breast reconstruction. Only patients who had a breast reconstruction classified as "excellent" from an objective (BCCT.core software) and subjective (questionnaire) point of view at the 6-month interval after the operation were included in the study. Data analysis highlighted a strong correlation between the volumes of the chosen prostheses and the weights of mastectomy converted into volume, especially for patients with grades B and C parenchymal density. The values of the agreement between the volumes of the chosen prostheses and the assessments from MRI and BREAST -V proved to be lower than expected from the literature. None of the four studied methods presented any strong correlation with the initial breast width. Our results suggest that conversion from weight to volume of mastectomy specimen should be used to assist in determining the volume of the breast implant to be implanted. This method would help the reconstructive surgeon guide the choice of the most appropriate implant preoperatively.