Fence Post Spacing: How Far Apart, and How Deep

Spacing by fence type

Eight feet on centre is the standard for wood privacy fence because rails come in 8 and 16 foot lengths and the arithmetic works out with no waste. Six foot spacing costs more in posts and concrete but produces a noticeably stiffer fence, and it is worth it on exposed sites and on anything over six feet tall.

Vinyl fence is not a spacing choice at all. The panels are manufactured to a fixed length, and the posts have routed slots that accept them — so the spacing is whatever the manufacturer says, usually six or eight feet, and it cannot be adjusted on site. Measure the run and plan the layout before digging a single hole.

Chain link stretches, so it tolerates wider spacing: up to 10 feet on residential fence, with terminal posts at every corner, gate and end doing most of the structural work. Those terminal posts are heavier gauge than the line posts and cost accordingly.

Depth: the rule and the exception

The working rule is one third of the above-ground height in the ground. A 6 foot fence wants 2 feet of post below grade, which means an 8 foot post. That gives an 8 foot post 6 feet up and 2 feet down, and it is why 8 foot posts are what the yard stocks.

The exception overrides the rule wherever the ground freezes. A post set above the frost line will be lifted by frost heave over a few winters no matter how much concrete surrounds it, and a heaved post takes a section of fence with it. Set below the local frost depth — which in the northern states can mean 3.5 to 4 feet, and therefore a 10 foot post on a 6 foot fence.

Gate posts are a separate case. A gate hangs its whole weight and every slam off one post, so gate posts go deeper, wider and in more concrete than line posts — commonly a 12 inch diameter hole rather than 8 or 10, and a foot deeper.

Counting posts without coming up short

A 100 foot straight run at 8 foot spacing needs 13 posts, not 12: twelve 8 foot bays span 96 feet and leave a 4 foot bay, and both ends need a post. The general form is the run divided by the spacing, rounded up, plus one.

Then add for geometry. Every corner is a post that belongs to two runs and must be counted once, every gate needs a post on each side, and every change in slope steep enough to break the rail line needs one. A rectangular yard fenced on three sides has four corner posts before a single line post is counted, which is why a fence around an irregular yard costs more per linear foot than a straight run of the same length.

This is the single biggest source of error in fence estimates, and it is worth running the actual layout — including corners and gates — through a calculator rather than multiplying a rate by the perimeter.

Concrete per hole

A 10 inch diameter hole 2 feet deep holds about 1.1 cubic feet of concrete, which is roughly two 50 lb bags of post mix once the post itself displaces some volume. A 12 inch hole 3 feet deep is about 2.4 cubic feet, or four to five bags. On a fence with 20 posts that is 40 to 100 bags — a pallet, not a trip in the car boot, and a line item people routinely forget.

Set posts in concrete with the hole belled slightly wider at the bottom than the top where frost is a concern, crown the concrete above grade so water runs away from the post, and leave a gravel base at the bottom of the hole for drainage on wood posts.

Common questions

How far apart should fence posts be?

Wood privacy fence: 8 feet on centre, or 6 for a stiffer fence and on tall or exposed runs. Vinyl: whatever the panel length is, typically 6 or 8, and not adjustable. Chain link: up to 10 feet.

How deep should a fence post be?

One third of the above-ground height, so 2 feet for a 6 foot fence — or below the local frost line if that is deeper. Gate posts go deeper still.

How many posts for 100 feet of fence?

Thirteen at 8 foot spacing on a straight run, before adding corners and gate posts. The formula is run ÷ spacing, rounded up, plus one.

How many bags of concrete per fence post?

Two 50 lb bags for a typical 10 inch by 2 foot line post hole; four to five for a 12 inch by 3 foot gate post hole. Buy by the pallet if the fence is any length at all.

In this topic

• Fence Cost Calculators
• Vinyl vs Wood Fence

  Twice the price for no maintenance, or half the price and a stain every few years. What each one does over twenty years, and which repairs are possible.

• Guides