Post-hole depth by above-ground post height
Typical industry planning values — NOT a structural/geotechnical design. Frost depth, soil, wind load and local code set the real post depth and footing; check your local building department and call 811 to locate utilities before you dig. A licensed engineer sizes load-bearing or high-wind fence posts.
A common planning rule sets the buried depth at about 1/3 of the above-ground height plus a 6" gravel base, with a hole diameter about 3× the post width. The values below are labeled planning typicals — NOT a structural or geotechnical design; frost depth, soil, wind load and local code set the real depth, and a licensed engineer sizes load-bearing or high-wind posts. Use this with the post-hole depth reference and the concrete-per-post calculator.
| Above-ground height | Buried depth (≈1/3) | Hole depth (+6" gravel) | Total post |
|---|---|---|---|
| 3 ft | 12 in | 18 in | 4.5 ft |
| 4 ft | 16 in | 22 in | 5.8 ft |
| 5 ft | 20 in | 26 in | 7.2 ft |
| 6 ft | 24 in | 30 in | 8.5 ft |
| 8 ft | 32 in | 38 in | 11.2 ft |
Labeled planning values — NOT a structural or geotechnical design. Frost depth, soil, wind load and local code set the real depth; a licensed engineer sizes load-bearing or high-wind posts. Call 811 to locate utilities before you dig.