How Deep Should Fence Posts Be?
A common rule is to bury about one-third of the post's total length: roughly 2 ft deep for a 6 ft fence on an 8 ft post. In cold climates, posts should reach below the local frost line. Holes are usually about three times the post width — 10–12 inches for a 4×4.
Post depth by fence height
| Fence height | Typical post length | Hole depth (approx.) |
|---|---|---|
| 3–4 ft | 6 ft | 2 ft |
| 5 ft | 8 ft | 2½–3 ft |
| 6 ft | 8 ft | 2–2½ ft |
| 8 ft | 10–12 ft | 3–4 ft |
Gate posts carry more load and are often set deeper and in bigger holes. Local codes and HOAs may set their own rules, and windy or exposed sites benefit from extra depth.
Concrete per post
| Hole (4×4 post) | 50 lb fast-setting bags | 80 lb mix bags |
|---|---|---|
| 8 in wide × 24 in deep | 1.4 | 0.9 |
| 10 in wide × 24 in deep | 2.5 | 1.5 |
| 10 in wide × 30 in deep | 3.1 | 1.9 |
| 12 in wide × 30 in deep | 4.7 | 2.9 |
| 12 in wide × 36 in deep | 5.6 | 3.5 |
Setting posts that last
- Call 811 before digging so utility lines are marked.
- Put a few inches of gravel in the bottom of the hole for drainage.
- Slope the top of the concrete away from the post so water runs off.
- Use posts rated for ground contact.
The fence calculator totals posts, rails, pickets and concrete for your whole fence.