The aim of this study was to assess the correlation between volumetric risk factors, orbital volume (OV), orbital volume ratio (OVR), herniated volume (HV), and the newly described herniated volume ratio (HVR), with the occurrence of late enophthalmos. Patients presenting a unilateral unoperated blow-out fracture were retrospectively included. OV and HV were measured using planimetry on the initial CT scan images. OVR and HVR were then calculated. Enophthalmos was measured on the 2-month follow-up CT scan images. The population was divided into two groups according to their enophthalmos status. Correlations and multiple linear regression model were used. 17 patients out of 45 presented a late enophthalmos of 1 mm or more. There were significantly higher OVR (107 (3.76); p < 0.0001), HV (0.8 (0.47); p < 0.0001) and HVR (3.3 (1.82); p < 0.0001) in the enophthalmos group. A very strong linear correlation between enophthalmos and OVR (rs = 0.806), HV (rs = 0.948) and HVR (rs = 0.951) was found. Enophthalmos prediction using these volumetric parameters can help the surgeon's decision-making in orbital blow-out fractures in order to prevent late enophthalmos. Measurement is simple and reproducible. However, larger prospective studies are needed to confirm these results.