Fence Calculator Widget
Give fencing suppliers and DIY readers a fence take-off. From the fence length, post spacing, gates, rails per section and picket size, the widget counts posts, rails and pickets and, if posts are set in concrete, the bags needed for every hole.
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<iframe src="https://a2z.tools/embed/w/fence-calculator" title="Fence Calculator by A2Z Tools" width="100%" height="960" style="border:0;width:100%" loading="lazy" allow="clipboard-write"></iframe>
A plain iframe. Works everywhere, including site builders that strip scripts. Adjust height if your content needs more room.
<div data-a2z-widget="fence-calculator" data-height="960"></div> <script async src="https://a2z.tools/embed.js"></script>
Adds a small script (what it does) that sizes the widget to fit its content, loads it lazily and keeps it isolated from your page's CSS.
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How it works
Gate openings are taken off the total length first; the remaining fence is divided by the post spacing and rounded up to whole sections. A straight run needs one more post than sections, and each gate adds one more because an opening splits the run and needs a post on both sides. Rails are sections times rails per section, and pickets are the fenced length divided by one picket plus its gap, rounded up - 96 ft of 5-1/2 in pickets with 1/2 in gaps takes 192. For concrete-set posts, each hole holds a cylinder of concrete minus the square post in it: a 10 in hole 24 in deep around a 3-1/2 in post takes 0.92 cu ft. That volume for all posts is divided by the bag yield (0.60 cu ft for an 80 lb bag of concrete mix, 0.45 for 60 lb, 0.30 for 40 lb; metric bags scaled by weight) and rounded up. A post wider than its hole or gates wider than the whole fence are refused.
Calculation method
- Fenced length = total length - gates x gate width
- Sections = ceil(fenced length / post spacing); posts = sections + 1 + gates
- Rails = sections x rails per section; pickets = ceil(fenced length / (picket width + gap))
- Concrete per hole = pi x (hole diameter / 2)^2 x depth - post width^2 x depth
- Bags = ceil(posts x concrete per hole / bag yield); 80 lb = 0.60 cu ft, 60 lb = 0.45, 40 lb = 0.30
Worked examples
Back-garden picket fence
Inputs: 100 ft; posts every 8 ft; 1 gate 4 ft; 2 rails; 5.5 in pickets with 0.5 in gaps; 10 x 24 in holes, 3.5 in posts, 80 lb bags
Result: 14 posts; 24 rails; 192 pickets; 22 bags
96 / 8 = 12 sections -> 13 + 1 posts; 96 x 12 / 6 = 192; 14 x 0.9207 cu ft = 12.89 / 0.60 = 21.5 -> 22.
Paddock post-and-rail
Inputs: 50 m; posts every 2.5 m; no gate; 3 rails; no pickets; no concrete
Result: 21 posts; 60 rails
50 / 2.5 = 20 sections -> 21 posts; 20 x 3 = 60 rails.
Limitations
- Models one straight run; corners, ends of separate runs and gate frames need adding by hand.
- Gates are counted as openings only - their own boards, hinges and latches are not included.
- Concrete assumes cylindrical holes and square posts; bell-shaped holes or gravel bases change the amount, and metric bag yields are scaled from a US data sheet.
Where publishers use it
- Fencing suppliers' product pages for picket, panel and post-and-rail fences
- Garden and smallholding blogs planning a boundary
- Pool-fence and pet-fence guides
- Fencing contractors' sites collecting a job size
- Farm and paddock fencing articles estimating posts per hundred feet or metres
Questions
How many fence posts do I need for 100 ft?
At 8 ft spacing with one 4 ft gate, 96 ft of fence makes 12 sections: 13 posts for the run plus 1 for the gate, 14 in all. Every extra corner or separate run adds a post.
What post spacing is normal?
6-8 ft (about 1.8-2.4 m) centre to centre for timber picket and privacy fences; panel fences use the panel width, often 6 ft or 1.83 m. Wider spacing saves posts but lets rails sag.
How deep should fence post holes be?
A common guide is one third to one half of the post's height above ground, and below the frost line in cold climates; check local rules. The widget uses whatever diameter and depth you enter.
How many bags of concrete per fence post?
A 10 in diameter hole 24 in deep with a 4x4 post holds 0.92 cu ft of concrete, about 1.5 bags of 80 lb mix at 0.60 cu ft per bag. For 14 posts that is 12.9 cu ft, or 22 bags.
How many pickets per foot of fence?
Divide 12 in by the picket width plus gap: 5-1/2 in pickets with 1/2 in gaps need 2 per foot, so 96 ft takes 192 pickets.
Does it handle panel or wire fences?
Yes - enter 0 for the picket width and the widget counts only posts and rails, with the post spacing set to the panel width.
What size posts and rails do I need?
Picket fences up to about 4 ft high commonly use 4x4 posts with 2x4 rails; 6 ft privacy fences often use 4x4 or 6x6 posts and three rails to stop the boards bowing. Corner, end and gate posts take more load and are often a size larger.
Should posts be set in concrete or gravel?
Concrete gives the stiffest footing and resists wind on solid privacy boards; compacted gravel drains better around timber and makes replacement easier. Many installers use a gravel layer at the bottom of the hole and concrete above it, crowned to shed water.
Sources
- Concrete Mix Product No. 1101 data sheet - QUIKRETE . Bag yields: 40 lb about 0.30 cu ft, 60 lb 0.45 cu ft, 80 lb 0.60 cu ft.
Cite or recommend this tool
If you reference this tool in an article, course or documentation, these formats are ready to copy. They are optional - nothing is added to your site unless you paste it.
A2Z Tools Fence Calculator https://a2z.tools/embed/fence-calculator
<a href="https://a2z.tools/embed/fence-calculator">A2Z Tools Fence Calculator</a>
[A2Z Tools Fence Calculator](https://a2z.tools/embed/fence-calculator)
Fence Calculator by A2Z Tools - https://a2z.tools/embed/fence-calculator
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