Fence Calculator
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About the Fence Calculator
A wood fence is a repeating unit — post, rails, pickets — so the whole materials list falls out of the length and three choices: how far apart the posts go, how many horizontal rails carry each section, and how the pickets are spaced. Getting the picket count right matters most; they're the largest line item and the easiest to under-buy when gaps enter the math.
Enter the run length, pick 6′ or 8′ post spacing (6′ resists wind and sag better; 8′ uses fewer posts), 2 or 3 rails (3 for 6′ privacy fences), and your picket width and gap. Standard dog-ear pickets are 5½″ wide; board-on-board privacy uses zero gap. The result is the full list: posts, rails, pickets, and concrete bags.
Setting posts in concrete and want the volume math instead of the bag rule? Use the Concrete Calculator
The Takeoff Math
Four lines cover the whole bill of materials:
Sections = ceil( length ÷ post spacing ) Posts = sections + 1 Rails = sections × rails per section Pickets = ceil( length in inches ÷ (picket width + gap) )
Worked example: 100′ of 6′-tall privacy fence at 6′ spacing = 17 sections → 18 posts and 34 rails (2 per section); with 5½″ pickets at ½″ gaps, 1,200″ ÷ 6″ = 200 pickets, plus about 36 bags of concrete at two per post.
Materials by Fence Length
Straight runs with 5½″ pickets, ½″ gaps, 2 rails per section — all rows computed by this calculator:
| Length | Posts (6′ / 8′ spacing) | Rails | Pickets |
|---|---|---|---|
| 50 ft | 10 / 8 | 18 / 14 | 100 |
| 100 ft | 18 / 14 | 34 / 26 | 200 |
| 150 ft | 26 / 20 | 50 / 38 | 300 |
| 200 ft | 35 / 26 | 68 / 50 | 400 |
| 300 ft | 51 / 39 | 100 / 76 | 600 |
Picket counts don't change with post spacing — only the structure (posts and rails) does. That's why 8′ spacing saves meaningful money on long runs.
Build Notes That Save Lumber
Small planning decisions with outsized material impact:
- Add a post at every corner, gate side, and grade change — the table above covers straight runs only.
- A 4′-wide gate consumes about 7 pickets plus hinge/latch hardware and its own 2×4 frame; price gates separately.
- On slopes, racked (parallel-to-grade) fencing wastes less lumber than stepped panels, but check that your rail stock is long enough for the true diagonal.
- Set posts with a third of their length in the ground as ballpark (2′ minimum for a 6′ fence) and always below your local frost line.
- Buy 5–10% extra pickets — culls, splits, and future repairs. Treated lumber shrinks; a snug ½″ gap today widens by itself.
Enter your supplier's per-piece prices against these counts and the whole fence budgets itself line by line.
Frequently Asked Questions
How many fence posts do I need for 100 feet?
At 6′ spacing: 18 posts (17 sections + 1). At 8′ spacing: 14. Add one more for each corner, gate, and significant grade change — those don't follow the straight-run math.
Should fence posts be 6 or 8 feet apart?
8′ is the economic standard and works for most panelized and picket fences. Choose 6′ for tall privacy fences in windy areas, heavy board-on-board designs, or where rails tend to sag — more posts means stiffer runs and shorter rail spans.
How many pickets per foot of fence?
Divide 12″ by picket-plus-gap: standard 5½″ pickets at ½″ gaps come to exactly 2 per foot (200 for 100′). Board-on-board (no gap) needs about 2.2 per foot, and 3½″ pickets at 1″ gaps about 2.7.
How much concrete per fence post?
The common rule is two 50-lb bags per post, which fills a 10–12″ diameter hole around a 4×4 at ~2′ depth. Bigger holes, deeper frost lines, or 6×6 posts push it to 3+ bags — the concrete calculator does the exact volume if you know your hole size.
How deep should fence posts go?
Rule of thumb: a third of the post's total length in the ground, with 2′ as the floor for a 6′ fence — and always below the local frost line so heave doesn't lift the posts. That's why 6′ fences use 8′ or 9′ posts.
How many rails does a fence need?
Two rails handle fences up to about 5′ tall; use three for 6′ privacy fences so pickets don't cup and the mid-span doesn't wave. Three rails on a 100′ run at 6′ spacing means 51 rails instead of 34 — the table shows both.
Methodology. This calculator uses standard construction and material-estimation formulas. It is reviewed and maintained by the Vast Calculators editorial team.
Last updated · July 2026
Results are estimates for general use; verify critical figures independently.