Background: Lumbar puncture’s (LP) success is dependent on the skill of the physician, anatomy, size, and posture of the patient. Aims: The purpose of this study was to describe a method that could be used to help estimate the correct depth of needle (Y) insertion in children based on age, weight (W), and height (H). Methods: The study consisted of 200 children American Society of Anesthesiologist class I–II aged 0–12 years who underwent spinal block for orthopedic, pediatric, and genitourinary surgery. The distance from the skin entry point to the tip of the spinal needle was measured after the LP was performed. The relationship between the Y and W, H and body mass index (BMI) was calculated. Predictive statistical models were used to determine the LP needle depth. A paired sample t-test was conducted to compare the findings of the developed model with those of earlier models. Results: The patients were aged 2–144 months, with H and W of 43–154 cm and 2.5–48 kg, respectively. The BMI was 10.75–37.72 kg/m2. Before the Y was estimated, the relationship between the independent variables and the depth variable, which was the dependent variable, was examined. According to the obtained results, the model consists of strong relationships with H, W, and H + W. The formula for predicting Y based on W plus H was as follows: for all patients: Y (cm) = 0.861 + 0.012 × H (cm) + 0.035 × W (kg). Based on H, the formula for predicting the required Y was as follows: For all patients: Y (cm) = 0.393 + 0.023 × H (cm). Based on W, the formula for predicting the required Y was as follows: For all patients: Y (cm) = 1.460 + [0.067 × W (kg)]. Conclusion: The formula may provide a more reliable estimate of the required LP depth in children than that obtained using current models. However, larger studies are needed to standardize the formula.