How many fence posts and pickets do I need?
A fence take-off is three quick counts. Divide the run by the post spacing for the number of sections; posts are sections + 1; rails are sections × rails per section; and pickets come from the run length in inches divided by the picket width plus gap.
The four formulas
Fencing is linear, so the counts are simple — the trick is remembering the “+1” on posts (a run of N sections has a post at each end).
sections = length ÷ spacing, rounded up
posts = sections + 1
rails = sections × rails per section
pickets = length (in) ÷ (picket width + gap), rounded up
Typical conventions: posts every 8 ft, a nominal 1×6 picket that is actually 5.5 in wide, a 1/4 in gap between pickets, and 2 rails per section (3 for tall privacy fences). The fence-materials tool uses these and lets you adjust them; the fence-spacing table lists them.
Worked example: a 100 ft fence
For a 100 ft run at 8 ft spacing, 2 rails per section, 5.5 in pickets with a 0.25 in gap:
- Sections = 100 ÷ 8 = 12.5, rounded up to 13.
- Posts = 13 + 1 = 14 posts.
- Rails = 13 × 2 = 26 rails.
- Pickets = (100 × 12) ÷ (5.5 + 0.25) = 1,200 ÷ 5.75 = 208.7, rounded up to 209 pickets.
That is the core bill of materials. Add posts for gates and for every corner and direction change, since those need their own posts regardless of spacing.
Why the “+1” on posts trips people up
Picture a short fence with two sections: post, section, post, section, post — that is three posts for two sections. Forgetting the +1 leaves you one post short at the end of every straight run, which is the single most common fence-math error. The tool handles it, but it is worth understanding.
Picket width and gap change everything
The picket count is sensitive to the width and gap you choose. A wider picket or a bigger gap covers the run with fewer pickets; a shadowbox or board-on-board style (overlapping pickets on alternating sides) uses far more. Because a “1×6” board is really 5.5 in, always use the actual width, not the nominal. For a solid privacy fence, set the gap to 0; for a spaced picket look, dial in the gap you want and watch the count change.
Rails, panels and hardware
Most fences use 2 rails per section; tall privacy fences add a third for stiffness. If you are buying pre-built panels instead of individual pickets, the count is just sections (one panel per section), with posts still sections + 1. Do not forget concrete for the post holes — size it with the post-hole concrete tool — plus screws or nails, post caps and gate hardware.
Corners, gates and end posts
The formulas assume a single straight run. Real yards turn corners and hold gates, and each of those needs its own post beyond the spacing math. A rule of thumb: add one post per corner and one extra per gate opening (a gate hangs between two sturdy posts, so a mid-run gate usually means an added post). Terminal (end) and gate posts also carry more load, so many installers set them deeper or larger. Sketch the perimeter, mark every corner and gate, and add those posts to the calculated line count.
Quick reference: posts and pickets by run length
At 8 ft spacing, 5.5 in pickets and a 0.25 in gap:
- 50 ft → 7 sections, 8 posts, about 105 pickets.
- 100 ft → 13 sections, 14 posts, about 209 pickets.
- 150 ft → 19 sections, 20 posts, about 313 pickets.
- 200 ft → 25 sections, 26 posts, about 418 pickets.
Picket counts assume a solid, gapless-to-0.25-in privacy layout; a spaced picket fence uses fewer, and a board-on-board or shadowbox style uses far more.
Setting posts that last
Post holes are typically dug about a third of the post’s above-ground height deep and below the frost line where it matters, then set in concrete. Size the concrete per hole with the post-hole concrete tool. Set the two end posts first, run a string line between them, and space the rest to the string so the fence runs true — a fence that wanders is almost always a fence whose posts were set by eye.
Once you have the take-off, estimate the spend with the fence cost tool from your own $/ft plus gates — see the fence cost guide. Every count here is a coverage estimate: confirm the actual picket width and buy a few extra pickets and a spare post for waste and mistakes.
Key takeaways
- Sections = length ÷ spacing; posts = sections + 1; rails = sections × rails per section.
- Pickets = length (in) ÷ (picket width + gap), rounded up — use the actual 5.5 in width.
- A 100 ft fence at 8 ft spacing needs 14 posts, 26 rails and about 209 pickets.
- Add a post for every corner and gate, beyond the straight-run spacing.
- Set post concrete with the post-hole tool and run a string line so the fence stays true.