Fence calculator
This counts materials for a straight run at the spacing and picket size you enter. It does not add posts for corners or gates, size the post footing, or set post depth for frost or wind — those are down to your layout and your local code. Walk the line and mark the openings before you buy.
Enter the length of the fence and your post spacing, and the tool splits the run into sections, counts the posts that bracket them, multiplies out the rails, and divides the run into pickets. Rails per section, picket width and the gap are all yours to set for the fence you are actually building.
Exemple détaillé
A 96 ft run at 8 ft spacing is 96 ÷ 8 = 12 sections, so 13 posts close the line. Three rails a section is 12 × 3 = 36 rails. With 5½-inch pickets and a ⅜-inch gap, each picket eats 5.875 inches, so 96 ft (1152 in) ÷ 5.875 ≈ 197 pickets. Add a post for each corner and gate on top.
In metric: a 30 m run at 2.4 m spacing is 30 ÷ 2.4 = 12.5, rounded up to 13 sections, so 14 posts and 13 × 3 = 39 rails. 140 mm pickets with a 10 mm gap take 150 mm each: 30,000 mm ÷ 150 = 200 pickets.
Sur le chantier
Two runs and a corner. A yard fenced 60 ft down one side and 40 ft across the back. Run them separately: 60 ÷ 8 = 7.5 → 8 sections, 9 posts; 40 ÷ 8 = 5 sections, 6 posts (in metric that yard is about 18.3 m and 12.2 m). The corner post is in both counts, so it is 9 + 6 − 1 = 14 posts. Rails 8 × 3 + 5 × 3 = 39. A 4 ft gate in the back run is its own bay with a post each side, so the 40 ft becomes 36 ft of fence plus a gate opening — the post count does not change, the pickets drop by about eight.
Even bays instead of a stub. 60 ft at 8 ft leaves a 4 ft last bay that looks like a mistake. Eight bays of 7 ft 6 in use the same nine posts and the rails are still cut from 8 ft stock — 6 in of offcut each. The tool counts posts off the rounded-up sections either way; the bay length is your call on site.
Pickets by the bay, not the run. On a fence where the pickets sit between the posts rather than over them, count per bay: an 8 ft bay is 96 ÷ 5.875 = 16.3, so 17 pickets with the gaps eased to fit. Twelve bays × 17 = 204, against 197 for a continuous run. Order the bay count plus a few, because the last picket in every bay is a rip.
Concrete for the holes. Fourteen holes at 10 in across and 30 in deep (250 mm × 750 mm): each is π × 5² × 30 = 2,356 in³ = 1.36 ft³ (0.039 m³), less the post itself (3.5 × 3.5 × 30 = 368 in³ = 0.21 ft³) — call it 1.15 ft³ a hole, 16 ft³ (about 0.46 m³) all told, about 27 bags at 0.6 ft³. The column tool does the cylinder for you.
What went wrong?
Quick referencefor a fence
- Posts on a straight run
- sections + 1 — sections = length ÷ spacing, rounded up
- Per 100 ft
- at 8 ft: 14 posts · at 6 ft: 18 posts · corners and gates extra
- Per 30 m
- at 2.4 m: 14 posts · at 1.8 m: 18 posts · corners and gates extra
- Traverses
- sections × rails per section
- Pickets per 8 ft bay
- 5½ + ⅜: 17 · 3½ + ½: 24 · 5½ tight: 18
- Concrete per hole, 10 in × 30 in
- about 1.15 ft³ net of the post — 2 bags at 0.6 ft³
- Métrique
- 2.4 m bays ≈ 8 ft · 140 mm picket + 10 mm gap = 16 per 2.4 m bay
Waste & overagewhat to add, and why
- Fence crews buy one extra post per run and a couple of extra rails for the panels that split or the post that goes in crooked; pickets carry 5–10% for the cull pile and the ones that split when nailed.
- Order posts a length longer than the fence height plus the burial depth you have chosen — a post that is exactly long enough is short once the hole is a touch deep.
Mistakes to catchbefore you order
- Forgetting the +1: a run of 96 ft at 8 ft spacing is 12 bays and 13 posts, not 12.
- Counting one long run when the fence turns three corners — each corner is a post shared by two runs, so add the runs and add one post per corner, not per run.
- Typing the picket width without the gap and then wondering why the count is high — the tool spaces pickets at width + gap.
What an inspector looks forthe municipal or bylaw inspector, and the building inspector where a permit applies
On this part of the job
- Height, measured from the grade the bylaw says to measure from — and that is often different on each side of a sloping lot.
- Location against the property line and any easement or sight-triangle rule at a corner. A fence on the wrong side of a line is a survey problem, not a carpentry one.
- Post embedment: depth and diameter against frost depth, and whether posts are set in concrete or in compacted aggregate.
- Pool and hot-tub enclosures, which are a separate and much stricter set of rules — spacing of infill, ground clearance, gate self-closing and self-latching hardware, latch height.
- Whether anything is being fixed to a shared or retaining structure that is not yours to fix to.
Have this ready
- A survey or real-property report showing the line, if there is any doubt at all.
- The bylaw's height and setback clauses, printed.
- Post holes open for the depth check before you set anything.
Every figure an inspector measures against comes from the code your jurisdiction has adopted, the stamped drawing, or the manufacturer's printed instructions — so none of them are printed here. Look the number up in your own book, type it into the tool, and the arithmetic is yours.
La formule
posts = ⌈length ÷ spacing⌉ + 1 · pickets = ⌈length ÷ (picket + gap)⌉
Dividing the run by the spacing and rounding up gives the sections; a straight run always has one more post than it has sections, because the last section still needs an end post. Rails scale straight off the section count. A picket plus its gap is the repeating unit along the run, so the run divided by it, rounded up, is the count.
Questions
- How many posts do I need for a fence?
- Divide the run length by your post spacing and round up to get the number of gaps, then add one for the closing post. A 96 ft fence at 8 ft spacing is 12 gaps, so 13 posts. Corners and gates need their own posts on top of that — add them to the count yourself, because only you know where they fall.
- What spacing should fence posts be?
- Eight feet on centre is the common default for wood fencing and is what this tool starts with, because it matches standard rail and panel lengths. Windy sites, heavy panels or chain link often go tighter; open wire can go wider. Set the spacing to your material and the post count follows.
- How many rails and pickets will a fence take?
- Rails are the number of sections times the rails per section — two for a short fence, three for a taller privacy fence. Pickets are the run length divided by one picket plus its gap, rounded up. Enter the picket width and the gap you want and the tool counts them; a butted board fence just uses a gap of zero.
- Does this include gates and corners?
- No — it counts the posts, rails and pickets for a straight run. Every corner and every gate opening adds a post, and a gate leaf is pickets you would otherwise have spanned, so treat those as separate line items. The tool gives you the run; you place the openings.
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