How this fence calculator works
A wood fence is four orders in one — posts, rails, pickets, concrete — and they all fall out of the run length and the post spacing:
pickets = length ÷ (picket + gap) × (1 + waste) · rails = sections × 3 over 4′ tall, × 2 under
At the defaults — 100 ft of 6 ft privacy fence at 8 ft on center — the order is 14 posts, 39 rails, 230 pickets and 28 bags of concrete, about $1,726 in materials; the full chain is in the worked example below. The two inputs that drive everything are the post spacing and the picket style — set those first.
The four parts of a wood fence
Every board fence is the same four orders, stacked from the ground up — get the count right on each and the fence is bought:
- Posts — the structure: 4×4s set in concrete every 6–8 ft; they carry the whole fence. Corner and gate posts often go 6×6 and deeper.
- Rails — the horizontals: 2×4 stringers spanning post to post — three per section above 4 ft, two below. Standard rails are 8 ft, which is why 8 ft spacing is common.
- Pickets — the face: the vertical boards — 5.5 in (1×6) butted for privacy, 3.5 in (1×4) spaced for a picket look. The style sets the count.
- Concrete — the footings: about two 80 lb bags per line post; price big holes on the sonotube calculator and rate the lumber on the board foot calculator.
Post spacing and how deep to set posts
Spacing sets the material count; depth sets whether the fence survives its first winter and windstorm. The working rules:
- Post spacing: 8 ft on center saves posts and suits 8 ft rails; 6 ft is stiffer for a tall privacy fence in wind.
- Post depth: a third of the fence height, never less than 2 ft, always below the frost line — a 6 ft fence wants 8 ft posts set ~2 ft deep.
- Hole width: about three times the post — a 4×4 wants a 10–12 in hole.
- Gate & corner posts: deeper, wider, and set in more concrete — they carry all the swing and turning load.
- Rails by height: two under 4 ft, three at 6 ft, so pickets can’t cup or sag between them.
How many fence posts and rails do I need?
| Run | Posts | Rails | Pickets | Concrete |
|---|---|---|---|---|
| 50 ft | 8 | 21 | 115 | 16 bags |
| 100 ft | 14 | 39 | 230 | 28 bags |
| 150 ft | 20 | 57 | 344 | 40 bags |
| 200 ft | 26 | 75 | 459 | 52 bags |
| 300 ft | 39 | 114 | 688 | 78 bags |
| Picket style | Count |
|---|---|
| Privacy — 5.5″ butted, no gap | 230 |
| Spaced — 5.5″ with 1.75″ gap | 174 |
| Spaced — 3.5″ with 3.5″ gap | 180 |
How to measure and lay out a fence
- Walk and measure each straight run in feet; total the legs separately and mark every corner and gate opening.
- Confirm the property line against the survey before you commit — a fence on the wrong side comes down.
- Set the post spacing — 6 or 8 ft on center — and the fence height from the layout guide.
- Pick the picket width and gap so the count matches the look — privacy, spaced, or board-on-board.
- Add a post at every corner, end and gate, then set the concrete bags per post to your hole size.
Worked example: materials for 100 feet of fence
The default, worked line by line — 100 ft of 6 ft privacy fence, 8 ft on center, 5.5 in pickets, 5% waste, two bags per post:
posts = 13 + 1 = 14 · rails = 13 × 3 = 39
pickets = (100 × 12 ÷ 5.5) × 1.05 = 229.1 → 230
concrete = 14 × 2 = 28 bags
cost = $920 + $252 + $351 + $203 = $1,726
The rails jump with height, not length: at 6 ft you get three per section, so the 13 sections take 39 rails where a 4 ft fence would need 26. And the straight-run post count is a floor — a real yard has corners and a gate or two, so add one post for each before you call the order in.
What this fence estimate doesn’t include
The four material lines are the bulk of a fence, but a finished job needs a handful of things the count leaves out:
- Gates. Hinges, a latch, and the heavier gate posts and frame — a hardware order of its own.
- Fasteners. Screws or nails, post caps and any brackets — small money, easy to forget.
- Finish. Stain or sealer, unless you run cedar and let it gray.
- Extra posts. The count is straight-run; every corner, end and gate adds one.
- Demolition. Pulling an old fence and busting out its concrete footings.
- Slope work. Stepping or racking the panels where the ground falls away.
Fence FAQ
How many fence posts do I need for 100 feet?
14 at 8 ft on center — 13 sections plus one post to close the run. Tighten to 6 ft spacing and it becomes 18. Corners and gates each take a post of their own, so walk the line and count every change of direction before ordering.
How far apart should fence posts be?
6 or 8 ft on center for a wood fence. 8 ft saves posts and concrete and suits standard 8 ft rails; 6 ft is stiffer and the better call for a 6 ft privacy fence in wind. Don’t stretch past 8 ft — rails sag and pickets loosen.
How deep should fence posts be set?
About a third of the fence height and never less than 2 ft, always below the local frost line — a 6 ft privacy fence wants 8 ft posts set roughly 2 ft into a hole three times the post width. Gate posts go deeper, in extra concrete, because they carry all the swing load.
How many pickets do I need for 100 feet of fence?
230 in solid privacy style — 5.5 in faces of 1×6 pickets butted tight, with 5% waste folded in. Space 3.5 in pickets with a 3.5 in gap and the same run takes 180; the gap does part of the covering.
How much concrete per fence post?
Two 80 lb bags per line post is the working figure for a 6 ft fence in a 10 in hole — 28 bags across the default 100 ft run. Use three at gates, corners and ends, and set the bags-per-post field to whatever your hole size actually takes.
How much does it cost to build a wood fence?
About $17 per foot in materials at the default prices — $1,726 for 100 ft of 6 ft privacy fence: $920 in pickets, $252 in posts, $351 in rails, $203 in concrete. Hired out, wood privacy fence commonly quotes at $25–55 per foot installed in 2026.
Sources and standards
Fence counts are lumberyard arithmetic; the setting depths are where local code takes over:
- Lumberyard practice: 6–8 ft post spacing, 8 ft rails, three rails above 4 ft and two below.
- Post-setting rule of thumb: a third of the fence height and below the frost line — local frost depth governs the hole.
- Concrete coverage: roughly two 80 lb bags per line post in a 10 in hole; the bags-per-post field sets the real figure.
- The survey: the property line and any HOA or setback rule govern where the fence can go — confirm before digging.
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