Penn state agricultural research and cooperative expansion is 36 inches typically fence post depth chart for line positions. Fences in areas with very sandy or wet soil must insert more deeply. Street posts and corner posts, which are often larger and under more pressure, are typically driven to a depth of 48 inches.
Following the mississippi state university extension service, the minimum depth for fence post must be related to their diameter and soil type. In loose, sandy soils, they recommend a position depth of 15 times of post diameter. In medium for heavy clay soil, they recommend sinking the position to a depth 10 times greater than the diameter of the position. For example, a 4-inch diameter post in heavy clay soil would have dropped to a depth of 40 inches.
While 36 inches for line positions and 48 inches for corner posts and gate positions are good rules fence post depth frost line of thumb, all factors must be considered. Soil type, size of fence posts, and the type of fence should all be taken into account to ensure that posts are solid. Ok, this article about fence post depth chart was enough. The end.