Quick Answer
Set wood fence posts at one-third of their total length below ground (minimum 2 feet for 6-foot posts, 3 feet for 8-foot posts). Dig holes 3–4 inches wider than the post diameter. Tamp soil in 6-inch layers, or pour concrete for corner and gate posts. Line posts lean slightly toward the inside of the fence; corner posts are plumb. Allow concrete to cure 24–48 hours before attaching wire.
Tools Required
- Post hole digger (manual, tractor-mounted, or gas auger)
- Level (4-foot level preferred)
- Tamping bar or mechanical tamper
- Tape measure and marking paint
- Concrete (60–80 lb bags, for corner posts)
Hole Depth Guidelines
| Post Length | Min Depth | Recommended Depth |
|---|---|---|
| 6 ft line post | 2 ft | 2 ft |
| 7 ft line post | 2.5 ft | 2.5 ft |
| 8 ft corner/gate post | 3 ft | 3–3.5 ft |
| Cold climate (below frost line) | Frost depth + 6" | 42–48 in (most US) |
Dry-Tamped vs. Concrete Setting
Dry-tamped (gravel or soil): Appropriate for line posts in stable soil. Fill hole in 6-inch layers, tamping firmly with a bar between each layer. Final 6 inches should be mounded above ground and sloped away from the post to drain water. Labor-intensive but avoids concrete cost (~$5–$8 per post).
Concrete: Required for corner posts, gate posts, and any post bearing significant lateral force. Mix one 60-lb bag per post hole (slightly damp). Pour around post, tamp to eliminate air pockets, and slope surface away from post. Concrete extends post life at the most vulnerable point — the soil-air interface where rot concentrates.
Common Mistakes to Avoid
- Setting posts too shallow: Wind load and livestock pressure will lean shallow posts within 1–2 years
- Concrete touching above-ground wood: Traps moisture and accelerates rot at the soil line
- Not checking plumb: Leaning posts look bad and compromise fence strength
- Skipping the string line: Without a string line, post alignment wanders visibly on long fence runs
Our Recommendation
Rent a tractor-mounted post hole auger for any project with 20+ posts — hand digging at the correct depth is exhausting and slow. Use concrete on corner and gate posts; dry-tamp line posts. Check plumb after every post. A fence with plumb, properly set posts lasts 20–30 years; a fence with shallow, unlevel posts needs repair in 5–10 years.