Global femoral offset (GFO) and femoral offset (FO) reportedly affect outcomes following total hip arthroplasty (THA). However, FO assessed using plain radiography is affected by internal and external rotations of the hip joint. We investigated the relationship between leg length discrepancy and Harris hip score (HHS), and their influence on acetabular offset (AO), FO, GFO, anterior femoral offset, and outcomes after THA. We retrospectively evaluated 140 patients with hip osteoarthritis who underwent THA. A three-dimensional (3D) pelvis and femur model created from computed tomography (data using ZedHip software was used to investigate these parameters. The modified (m)HHS scores were significantly improved from 49.0 to 88.8 in total mHHS, 20.0-44.5 in pain, and 28.9-44.4 points in function. Significant correlations were found between the differences in AO, FO, GFO, and pain score in binominal, with maximum values of - 1.24, + 1.54, and + 0.90 mm/100 cm body height, respectively. The maximum value of GFO and mHHS in binominal was + 1.17 mm/100 cm body height (BH). The optimal range of difference of GFO was - 1.75 to 4.09 mm/100 cm BH. This is the first report using a 3D method for assessing FO. Preoperative planning using the system could improve postoperative function.