Fence Calculator
Count fence posts, rails, pickets or panels and concrete bags for one or more straight runs with gates and corners, plus post length and material cost.
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About this toolWhat is the Fence Calculator?
A fence estimate starts with the oldest counting trap in arithmetic: a straight line divided into sections has one more post than sections. Add a gate and the line splits in two with a gate between them, which adds a post. Add a corner and the next run starts from a post you already counted. This fence calculator handles all three by working run by run, so the post count is the one you will actually set in the ground.
Describe the fence as straight runs, one per side, and say how many gates each run has. Choose a stick-built fence of rails and pickets or prefabricated panels, set the post spacing (or panel width), and the calculator returns posts, sections, rails, pickets or panels, the post length, and the concrete for every hole in bags of the size you buy.
Prices per post, rail, picket, panel and bag give a material cost. A table shows each run with its sections and actual section length, which is the number you use to lay out the post line with a string.
- Any number of straight runs with gates, open or closed layouts
- Rails and pickets or prefabricated panels
- Concrete per post and in total, in 40, 50, 60 and 80 lb or 20 and 25 kg bags
- Run-by-run table with the real section length for layout
- Material cost and post length; runs in the browser with a share link
How to use the Fence Calculator
- Choose imperial or metric. Long lengths are feet or metres; picket width, post size and hole size are inches or millimetres.
- Pick rails and pickets or prefabricated panels.
- Add one row per straight run of fence with its length and the number of gates in it, and say whether the fence ends at a house or closes on itself.
- Set the gate width, post spacing (or panel width), fence height and, for picket fences, rails per section, picket width and gap.
- Enter post size, hole diameter and depth and the concrete bag you will buy, then add prices for a material cost.
Worked examples
100 ft privacy fence with a gate
Input
One 100 ft run, one 4 ft gate, 8 ft spacing, 6 ft high, 3 rails, 5.5 in pickets, no gap, 5% extra
Output
14 posts, 12 sections, 38 rails, 227 pickets, 22 bags of 80 lb concrete
The 96 ft of fence splits into two 48 ft pieces of six 8 ft sections each. Twelve sections plus the gate need 14 posts. Each section takes ceiling(96 / 5.5) = 18 pickets.
Three sides of a back yard
Input
Runs of 50, 100 and 50 ft, no gates, open at the house
Output
27 sections and 28 posts
The 50 ft sides need 7 sections each and the back needs 13. The two corner posts are shared, so the total is sections plus one.
Concrete for one post
Input
4x4 post (3.5 in), 10 in hole, 24 in deep
Output
0.92 ft³ per post, two 80 lb bags
The hole holds 1.09 ft³ and the post displaces 0.17 ft³. One 80 lb bag makes 0.6 ft³, so each post needs a second bag.
Background and insight
Post spacing is a maximum, not a rule that every section must hit. Wood privacy fences are commonly built with posts 6 to 8 feet on centre, because 8 foot rails are a stock length and longer spans sag. When a run does not divide evenly, the calculator rounds the number of sections up and spreads the length evenly, so a 50 foot run at 8 foot maximum spacing becomes 7 sections of 7.14 feet instead of six full sections and a stub.
Gates are assumed to be spaced evenly within their run. That gives the fewest posts; a gate placed off-centre can need one more section on one side, so check the run table against your plan. Each gate needs its own pair of posts, which should be set deeper or larger because a swinging gate loads the hinge post sideways.
Concrete is the hole volume minus the part of the hole the post fills. A common rule from post and concrete manufacturers is a hole about three times the post width and at least a third to a half as deep as the post stands above ground, and always below the local frost line so frost heave cannot lift the post. Bag yields come from published data: an 80 lb bag of concrete mix makes about 0.60 cubic feet and a 50 lb bag of fast-setting mix about 0.375 cubic feet.
Common use cases
Privacy and picket fences
Get the post, rail and picket list for a wood fence before ordering lumber.
Panel fences
Count vinyl or wood panels and the posts between them for a yard with several sides.
Gates and corners
See how gates and changes of direction change the post count instead of guessing.
Concrete order
Buy the right number of bags for every post hole in one trip.
Tips and limitations
- Call your local utility locator before digging post holes.
- Check frost depth and any height limits in your local code or homeowners association rules before you buy posts.
- Set corner, end and gate posts first, run a string line between them, then fill in the line posts.
- Fence boards shrink and split. A few percent of extra pickets saves a second trip.
- Panels must fit between posts, so measure the actual panel width plus post width before setting the spacing.
Frequently asked questions
How many fence posts do I need for 100 feet?
At 8 foot spacing a straight 100 foot run without gates needs 13 sections and 14 posts. With one 4 foot gate it still needs 14 posts: 12 sections of fence plus the gate opening, because the gate adds a post.
How far apart should fence posts be?
Most wood fences use 6 to 8 feet between post centres. Eight feet matches stock rail lengths; closer spacing is stiffer and suits tall fences, heavy boards or windy sites. Panels set the spacing to the panel width.
How many bags of concrete per fence post?
A 10 inch hole 2 feet deep around a 4x4 post needs about 0.92 cubic feet, so two 80 lb bags. Fast-setting 50 lb bags make about 0.375 cubic feet each, so three of those. Wider or deeper holes scale up quickly.
How deep should a fence post hole be?
A common rule is a third to a half of the post height above ground, so 2 to 3 feet for a 6 foot fence, and always below your frost line. Gate posts benefit from the deeper end.
How many pickets do I need per 8 foot section?
Divide the section length by the picket width plus gap. A privacy fence of 5.5 inch boards touching each other needs 96 / 5.5 = 17.5, so 18 per 8 foot section. With a 2.5 inch gap and 3.5 inch boards it is 16.
Do corners add extra fence posts?
A corner post is shared by the two runs it joins, so it is counted once. Corners only add posts because each run is rounded up to whole sections on its own, which the calculator does run by run.
Is there an in-depth guide to the Fence Calculator?
Yes. “How to Estimate Fence Posts, Pickets, Rails and Concrete” covers the background, how it works, common pitfalls and worked examples. Read the full guide.
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