Fence Material Calculator
Enter your total run and post spacing to size a wood fence in seconds: how many posts, how many rails, and how many pickets to buy — with the picket count driven by the picket width and the gap between boards.
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A 100 ft fence at 8 ft spacing needs about 14 posts, 26 rails and 209 pickets. Add posts for gates and corners; spacing and picket width are labeled typicals you can adjust.
A fence take-off is really three counts that all start from the run length. Space the posts evenly along the line, hang rails (stringers) between each pair of posts, and then fill the sections with pickets set at a fixed pitch (board width plus the gap). Get those three numbers right and the lumber list writes itself.
The single most common question this answers: how many posts and pickets for a 100 ft fence? At 8 ft spacing that is 14 posts and about 209 pickets (5.5 in boards with a 0.25 in gap) — the worked example below shows every step. Add posts for gates, corners and any change of direction, since each of those needs its own post beyond the straight-run count.
Formula
Sections come from the run divided by the spacing, rounded up so the last (short) bay still gets its own post:
sections = ceil(length_ft ÷ post_spacing_ft) posts = sections + 1 rails = sections × rails_per_section pickets = ceil(length_ft × 12 ÷ (picket_width_in + picket_gap_in))
The +1 on posts is the classic fence-post rule: a straight run of n sections always has n+1 posts (one at each end plus the shared posts between bays). Pickets use the pitch — the board width plus one gap — so a tighter gap means more boards. This is a straight-run estimate; add one post per gate opening and per corner.
Worked example
Take a 100 ft back fence at 8 ft post spacing, 2 rails per section, 5.5 in pickets and a 0.25 in gap:
- Sections: ceil(100 ÷ 8) = ceil(12.5) = 13 sections
- Posts: 13 + 1 = 14 posts
- Rails: 13 × 2 = 26 rails
- Pickets: 100 × 12 = 1,200 in; pitch = 5.5 + 0.25 = 5.75 in; 1,200 ÷ 5.75 = 208.7 → 209 pickets
So a plain 100 ft run needs 14 posts, 26 rails and about 209 pickets — then bump the posts up for the gate and any corners. Buy a few extra pickets for culls and cuts.
Fence take-off in practice
Post spacing. Six to eight feet is the usual range. Eight-foot bays use fewer posts and match 8 ft rail stock with no waste; six-foot bays are stiffer and better for tall privacy panels or windy, exposed runs. The spacing here is a labeled typical you can change to match your rail length and local wind conditions.
Rails. Short and mid-height fences use two rails (top and bottom); privacy fences six feet and taller usually get a third rail in the middle to keep the pickets flat. If you buy rail stock that spans two bays, divide the rail count by the boards-per-run you actually cut.
Pickets. A "1×6" picket is really 5.5 in wide, and a "1×4" is 3.5 in — always use the actual dressed width, not the nominal name. A 1/4 in gap is common for board fences; set the gap to 0 for a solid privacy fence, or use a wider gap for a shadowbox/board-on-board look (which uses noticeably more boards because the pickets overlap). Order a handful extra to cover knots, splits and trim cuts.
Posts, concrete and gates. Every gate opening needs a post on each side, and each corner or jog in the line adds a post beyond the straight-run number. Once you have the post count, size the bagged concrete for the holes with the post-hole concrete calculator, and price the whole job with the fence cost calculator.
Reference table
Common post spacings (labeled planning typicals — match your rail length and wind exposure):
| Post spacing | When to use it |
|---|---|
| 6 ft | Stiff runs, tall privacy, windy sites |
| 7 ft | A middle-ground compromise |
| 8 ft | Standard — matches 8 ft rail stock, fewest posts |
Picket pitch = board width + gap. A 1×6 is 5.5 in wide; a 1×4 is 3.5 in.