Fence Post Depth Calculator

Estimate post-hole depth, hole diameter, required post length, and concrete for a fence project. Local building codes and frost-depth requirements always take priority.

Fence Information

Finished Fence Height (feet)

Number of Posts

Post Size or Type

Hole Requirements

Local Frost Depth (inches)

Enter 0 if frost depth does not apply or is unknown. Check local requirements before digging.

Gravel Base Depth (inches)

Hole Diameter

The automatic estimate uses a hole approximately three times the post width and rounds up to a practical whole-inch diameter.

Concrete Details

Concrete Fill

Concrete Bag Size

Extra Concrete Allowance (%)

Bag yields vary by product. Use the yield printed on your concrete bag when purchasing material.

How Hole Depth Is Estimated

A common planning rule is to bury approximately one-third of the post’s above-ground height. The calculator also compares that estimate with the entered frost depth and uses the deeper requirement.

The gravel base is added below the buried post when determining the total excavation depth. Local codes, gate-post requirements, wind exposure, soil conditions, and fence design may require a deeper or wider hole.

Before You Dig

Contact 811 before digging so underground utilities can be marked.
Confirm local frost depth, permit rules, setbacks, and fence-height restrictions.
Gate, corner, and end posts may need larger holes than ordinary line posts.
Verify available post lengths before purchasing materials.
Follow the concrete manufacturer’s water and curing instructions.

Results are planning estimates, not structural or code requirements. Soil, drainage, frost, wind, fence material, gate loads, post type, and local codes can change the required installation. Confirm the final design with local authorities and product instructions.