Fence Post Depth and Spacing: How Deep and How Far Apart
A fence is only as strong as its posts. Posts that are too shallow lean and rock in the wind, while posts that are too far apart sag and cost you rails and pickets in the long run. This guide covers the common guidelines for depth, spacing and setting posts, so your fence stands up for years.
Before you dig
Check property lines, homeowners association rules and whether you need a permit. In the United States, call 811 a few days before you dig so buried utility lines are marked. Never dig first and ask later.
How far apart should posts be?
For wood fences, 6 to 8 feet between posts is typical, and 8 feet is common because lumber is often sold in 8-foot lengths. Choose closer spacing for tall privacy fences in windy areas, and for sections next to a gate, which carry extra weight. A fence always needs one more post than it has sections.
For a 100 foot fence with 8-foot spacing, that means 13 sections and 14 posts. Our fence calculator counts posts, rails and pickets for your exact length and lets you change the spacing.
How deep should posts be?
A common rule is to bury at least one third of the post's total length. In places where the ground freezes, local code may require posts to reach below the frost line, so check with your building department.
| Fence height | Typical post length | Typical burial depth |
|---|---|---|
| 4 ft | 6 ft | About 2 ft |
| 6 ft | 8 ft | About 2.5 to 3 ft |
Dig the hole about three times as wide as the post. A 4×4 post usually goes in a hole around 10 to 12 inches across.
Setting the post
- Add a few inches of gravel at the bottom of the hole for drainage.
- Set the post and check it with a level on two adjoining sides.
- Brace it so it cannot move while the concrete sets.
- Fill with concrete, or with compacted gravel if you prefer that approach.
- Slope the top of the concrete away from the post so water runs off.
A 10-inch-wide hole about 30 inches deep holds roughly 1.3 cubic feet of concrete around a 4×4 post, which is about two 80-lb bags of mix, or three to four 50-lb bags. Wait for the concrete to harden, commonly a day or two, before you attach rails.
Mistakes to avoid
- Skipping the call to 811
- Setting posts too shallow to save digging time
- Burying wood that is not rated for ground contact
- Not bracing posts while the concrete cures
- Spacing posts evenly by eye instead of measuring
Measure the full run first, divide it into equal sections no longer than your chosen spacing, and mark every hole before you dig. That keeps the fence straight and the post count accurate.
Enter the length of your fence to see how many posts, rails and pickets to buy.
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