Introduction: Liver volumetry based on a CT-Scan is widely used for estimating liver volume before any liver resection, especially for pediatric living donor liver transplantation (LDLT). The "One-to-one" conversion rule for liver volume to weight has been widely adopted worldwide for many years. However, most recent analyses discuss this approach. Methods: The study retrospectively included consecutive donors undergoing left lateral hepatectomy for pediatric LDLT between December 2008 and September 2020. All donors were healthy adults who met the evaluation criteria for pediatric LDLT and underwent a preoperative contrast-enhanced CT scan. Manual segmentation of the left lateral liver lobe for volume (GV) estimation and intraoperative measurement of an actual graft weight (AGW) was performed. A relationship between estimated GV and AGW was analyzed. Results: 94 living liver donors were included in the study. The mean AGW was approximately 283.4 ± 68.5 grams, and the mean GV was 244.9 ± 63.86 ml. There was a strong correlation between the GV and AGW (r = 0.804, p < 0.001). The Bland-Altman analysis revealed an interreader agreement of 38.0 ± 97.25 and an intraclass correlation coefficient showed an almost excellent agreement (0.840, p < 0.001). The conversion formula for calculating graft weight (GW) based on computed tomography volumetry was determined based on regression analysis: 0.88 x GV + 41.63. Conclusion: Estimating left liver GW using "one-to-one" rule is subject to measurable variability in calculated graft weights and tends to underestimate it. Instead, a conversion formula should be used to determine donor GW more accurately.