Fence Calculator
With fence length 100 ft, post spacing 8 ft, picket width 5.5 inch, gap between pickets 0 inch and 1 more field, fence comes to 14 posts — posts. It is reached in 5 steps, the last of which is 13 + 1, and each one is printed on the page with its numbers filled in. The formula is the one published by American Fence Association, not an approximation fitted to it.
Posts, rails, pickets and concrete for a run of fence at a given post spacing. Sections, posts, rails, pickets and the two bags of concrete each post takes.
Formula and sources checked · How we check
Fence length 100 ft, Post spacing 8 ft, Picket width 5.5 inch, Rails per section 3
14 posts
Posts for the example below. Editing a field recomputes the calculator below; this figure holds the answer the page was loaded with.
It is written into the HTML rather than drawn by a script, so a search engine reading this page without running JavaScript still finds an answer.
- Sections
ceil(100 / 8)13 sections- Posts
13 + 114 posts- Rails
13 * 339 rails- Pickets
ceil(100 * 12 / (5.5 + 0))219 pickets- Concrete (two 50 lb bags per post)
14 * 228 bags
Several at once
A job is rarely one of anything. Work out the first, add it, change the figures and add the next — the list keeps what each line was, and totals them.
Worked example
100 ft at 8 ft spacing is 13 sections, so 14 posts — the extra one is the far end, and forgetting it is the most common fence-order mistake. That run takes 39 rails, 219 pickets and about 28 bags of concrete.
How to work it out yourself
- 1.Measure the total run of fence in feet and pick a post spacing — 8 ft standard, 6 ft for tall or windy sites.
- 2.Divide the run by the spacing and round up for the number of sections, then add one for the number of posts.
- 3.Multiply sections by rails per section, usually three for a privacy fence.
- 4.Divide the run in inches by picket width plus gap for the picket count.
- 5.Allow two 50 lb bags of concrete per post, and set corner and gate posts deeper than line posts.
The formula
- Sections
ceil(100 / 8) - Posts
13 + 1 - Rails
13 * 3 - Pickets
ceil(100 * 12 / (5.5 + 0)) - Concrete (two 50 lb bags per post)
14 * 2
Source: American Fence Association, American Wood Council — wood construction data
Questions people actually ask
- Why is it posts = sections + 1?
- Every section needs a post at each end and neighbouring sections share one, so thirteen sections have fourteen boundaries. The same off-by-one applies to fence panels, deck balusters and anything else laid end to end.
- How deep should the posts go?
- A third of the above-ground height, or below the local frost line — whichever is deeper. A 6 ft fence wants 2 ft of post in the ground, and in a cold climate the frost line usually wins.
- Do I need concrete on every post?
- End, corner and gate posts always — they carry the tension. Line posts can be set in compacted gravel, which drains better and rots the post more slowly than concrete that holds water against the wood.
Related
- Concrete CalculatorCubic yards of concrete for a slab, round pad, footing, column, wall or stairs, with bag counts and cost.
- Board Foot CalculatorConvert lumber dimensions to board feet and price out a cut list, including nominal-vs-actual sizing.
- Roofing CalculatorRoofing squares and shingle bundles from the building footprint and the roof pitch. Applies the pitch multiplier, so it is roof area, not footprint.
- Siding CalculatorSquares of siding for a house from its wall dimensions, with openings deducted and waste added.
Read first
- What a Fence Costs — Post spacing, the ground-contact rating most people buy wrong, and why corners and gates cost more per foot than the long straight runs between them.
Put this calculator on your site
Free, no attribution required beyond the link.
<iframe src="https://rulecalculators.com/embed/fence-materials" width="100%" height="420" style="border:1px solid #e7e4de;border-radius:12px" title="Fence Calculator"></iframe>