How many fence posts do I need per 100 feet?

At 8-foot spacing, 100 feet divides into 13 sections, which takes 14 posts — one more than the sections, because both ends of an open run need a post. At 6-foot spacing it is 17 sections and 18 posts.

What post spacing should I use?

8 feet is standard for privacy fences with prefab panels; 6 feet stiffens the fence in windy sites or with heavier boards. Rail lumber lengths matter too — 8- and 16-foot rails divide evenly over 8-foot bays.

How many bags of concrete does each fence post take?

A typical 4×4 post set 2 feet deep in an 8-inch hole takes about half a cubic foot of mixed concrete once the post displaces its share — roughly one and a half 50 lb bags. The calculator rounds the total up to whole bags.

How do gates change the material count?

A gate occupies one section between two posts, so it consumes spacing but no rails or pickets — those come with the gate kit. Gate posts are often upgraded to 6×6 and set deeper, which is worth the small extra cost.

How many pickets per foot of fence?

Divide 12 inches by picket width plus gap. Standard 5.5-inch boards butted tight run about 2.2 per foot; with a 2-inch gap it drops to 1.6. Board-on-board coverage overlaps and needs roughly 30% more.

Fence Calculator

Count posts, rails, pickets and concrete bags for a fence run — with the fencepost rule applied correctly and gates handled as hardware.

The Fence Calculator runs entirely in your browser. Your measurements are processed on your device and never uploaded.

Open the Concrete Calculator

About Fence Calculator

Fence Calculator gets the counting details right that a quick sketch gets wrong. An open run needs one more post than it has sections — the classic fencepost rule — so 100 feet at 8-foot spacing is 13 sections and 14 posts, not 12 and 12. Rails multiply by panel sections only, because a gate opening consumes a section but takes no rails or pickets; the gate arrives as hardware. Pickets fill the un-gated length at a pitch of picket width plus gap, and each post hole needs concrete — figured here at half a cubic foot per post and converted into 50 lb bags, the unit the store actually sells. Enter your run in feet or metres and read off a materials list you can take to the yard.

Features

Fencepost rule applied correctly: sections plus one post
Gates consume sections without adding rails or pickets
Rails per section configurable for 2-rail and 3-rail designs
Picket count from width and gap, including board-on-board zero gap
Concrete per post hole converted to 50 lb bags
US and metric input
Copyable materials summary
Everything computed on your device

How to use the Fence Calculator

Enter the total fence run and post spacing
Add the number of gates and rails per section
Set picket width and gap — or width 0 for a rail-only fence
Read posts, rails, pickets and concrete bags

Example

Input

100 ft run · 8 ft spacing · 1 gate · 2 rails · 5.5 in pickets, no gap

Output

14 posts · 24 rails · 210 pickets · 7 bags of concrete

The gate section keeps its two posts but adds no rails or pickets.

Common errors & troubleshooting

The post count is one higher than sections × spacing suggested. — That is the fencepost rule. A run of N sections has N+1 posts because both ends need one — the oldest off-by-one error in mathematics, avoided here on purpose.
A closed loop like a full garden perimeter shows one post too many. — A closed ring has exactly as many posts as sections since the last post is the first. Subtract one post from the result when your fence returns to its starting point.
Bought pickets ran out before the fence was done. — Add 5–10% for cuts, splits and culls — lumber yards include boards you will reject. The calculator gives the geometric count; the buffer is yours to add.
The concrete estimate seems low for large posts. — Half a cubic foot suits a standard 4×4 post in an 8-inch hole at 2 ft depth. Bigger holes, deeper frost lines or 6×6 posts need more — scale the per-post figure to your hole size.

Frequently asked questions

How many fence posts do I need per 100 feet?: At 8-foot spacing, 100 feet divides into 13 sections, which takes 14 posts — one more than the sections, because both ends of an open run need a post. At 6-foot spacing it is 17 sections and 18 posts.
What post spacing should I use?: 8 feet is standard for privacy fences with prefab panels; 6 feet stiffens the fence in windy sites or with heavier boards. Rail lumber lengths matter too — 8- and 16-foot rails divide evenly over 8-foot bays.
How many bags of concrete does each fence post take?: A typical 4×4 post set 2 feet deep in an 8-inch hole takes about half a cubic foot of mixed concrete once the post displaces its share — roughly one and a half 50 lb bags. The calculator rounds the total up to whole bags.
How do gates change the material count?: A gate occupies one section between two posts, so it consumes spacing but no rails or pickets — those come with the gate kit. Gate posts are often upgraded to 6×6 and set deeper, which is worth the small extra cost.
How many pickets per foot of fence?: Divide 12 inches by picket width plus gap. Standard 5.5-inch boards butted tight run about 2.2 per foot; with a 2-inch gap it drops to 1.6. Board-on-board coverage overlaps and needs roughly 30% more.

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