The issue regarding errors in the depth of a refractor owing to masked or undetected layers in the overburden is a drawback of the seismic refraction method. The solutions available for eliminating these errors require prior knowledge of the masked layers. These solutions are not useful when several unknown masked layers occur, such as in sedimentary basins. The use of the average velocity of the overburden above the refractor has been suggested by early investigators to reduce these errors. However, no quantitative relationship between the average velocity-based depth and the actual depth has been established. Subsequent studies have shown that the average velocity-based depth is invariably lower than the actual depth. Therefore, it can be considered the minimum depth, irrespective of the number, type, velocity, and thickness of the masked layers present in the overburden.This study shows that the minimum depth to a refractor obtained using the average velocity of the multilayer overburden and the intercept time closely approximates the actual depth with a minor (< 10%) error. The maximum limit of error for all practical purposes is −14.6%, but not substantially higher as previously expected. These findings hold fundamental significance. The expression derived for the error in the three-layer case clearly indicates that it varies (a) directly as the square of the difference between the velocities of the top and intermediate layers and (b) inversely as the velocity of the refractor below them. The error also has an inverse relationship with the composite term comprising the sum of the, velocity ratio to the thickness ratio of the intermediate layer to the top layer, as well as its reciprocal. Numerical modeling with synthetic models and a multilayer field example with a hidden layer were used to illustrate these findings. This study highlights the vital role that the average or root mean square velocity can play in refraction seismics.