Fence calculator: how many posts, rails and pickets?
This fence calculator counts what to buy for a wood board fence. Enter each straight run, any gate, the height and your post spacing. You get posts by role, rails, pickets, fasteners and bags of post concrete, and the spacing each run really gets. Every count is rounded up, with waste added first where it applies.
Runs
Each run is one straight line. Its length is measured center to center of the two posts at its ends. Consecutive runs meet at a shared corner post. Measured the outside of the end posts? Subtract one post width.
A gate sits at the far end of its run. Enter the gate opening plus one post width.
Run 1
Run 1
posts
Waiting for a run length.
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Waiting for a run length.
Run lengths are center to center of the posts at each end.
Every count is rounded up, with waste added first where it applies.
Rails by height: calcshed.com and calcsummit.com, read 27 Sep 2026. Rails join on posts: America's Fence Store, read 27 Sep 2026. Lumber sizes: American Softwood Lumber Standard (PS 20). Bag yields: QUIKRETE, approximate. Post spacing 8 ft: Hoover Fence's default, read 26 Sep 2026.
The five percent waste and the 2 fasteners per picket per rail are our starting figures, not sourced ones. Change them to suit your project.
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How does the calculator space the posts?
Posts on each run are set at equal spacing, no wider than the maximum you enter. The default maximum is 8 ft.
Take one 100 ft run, 4 ft high. 100 ft is 1,200 in, and 1,200 / 96 is 12.5, so you need 13 sections. Split evenly, that's 7 ft 8-5/16 in (92.31 in) between post centers. It takes 14 posts: 2 end posts and 12 line posts.
When a run divides evenly, nothing is rounded. A 96 ft run gives 12 even sections at 8 ft 0 in and 13 posts.
Run lengths are center to center of the posts at each end. If you measured to the outside of the end posts, subtract one post width before you enter the run.
How are corners and gates counted?
Two runs that meet share a corner post, so it's counted once. Four runs of 25 ft laid out as a closed loop take 16 posts: 4 corners and 12 line posts. Leave the same four runs open at the ends and it's 17: 2 end, 3 corner and 12 line.
A gate sits at the far end of its run. For a gate partway along a line, enter that line as two runs, with the gate at the end of the first. Enter the gate bay, which is the gate opening plus one post width. The bay adds one gate post and comes out of the run's fence, so a 40 ft run with a 4 ft gate bay has 36 ft of fence, set in 5 sections at 7 ft 2-3/8 in. A post that borders a gate is counted as a gate post, never twice.
How many rails and pickets will you need?
Rails start at one per 24 in of fence height, rounded up, with at least 2. That's the rule calcshed.com and calcsummit.com print, and we cap it at 4 per section. That's 2 on a 4 ft fence, 3 on 5 or 6 ft, and 4 on 7 or 8 ft. You can pick a different number and it'll stay put.
On the 100 ft run at 4 ft, 13 sections x 2 rails is 26 rails of 8 ft stock. Raise the same fence to 8 ft and it's 4 rails a section, so 52. Rails can't join between posts, so longer stock pays off when two whole sections fit on one board. With 16 ft rails the 4 ft fence needs 14.
For pickets, add any gap to the picket width, then divide the fence length by that total and round up for each run. With 1x6 pickets (5.5 in actual) and no gap, the 100 ft run takes 219. At 2 fasteners per picket per rail, that's 876 fasteners. The 2 is our starting figure, not a sourced one, so change it to match your plan.
How is waste added?
Waste multiplies the picket and rail totals, and then the page rounds up. Our starting figure is five percent. It's a default, not a published standard, so change it to suit your supplier and your cuts.
At five percent the 100 ft run needs 229.95 pickets, so you buy 230. Rails go from 27.30 to 28. The page shows the figure before rounding beside each one. Waste isn't added to posts, fasteners or concrete.
How much concrete per fence post?
Enter the hole diameter and depth, and the page works out the concrete around each post. The post fills the hole to full depth. With a 10 in by 24 in hole around a 4x4 post, that's 0.92 cu ft per post and 12.89 cu ft for 14 posts, or 22 bags of 80 lb. The total uses the unrounded 0.9207 cu ft per post, which is why it isn't 0.92 x 14.
Bag yields are the same ones our concrete calculator uses. For a slab or footing rather than post holes, use that page. For more on waste allowances, see how much waste to add.
What this doesn't do
It counts materials for a board fence made of straight, level runs. The runs you enter join end to end, so for two separate stretches of fence, work out each one on its own. It doesn't handle panels, chain link, wire or vinyl, sloped or stepped sections, or the gate leaf and hardware. It doesn't recommend a post depth or look up any price. You can type in your own prices, and the cost is worked out from the counts you buy. More tools are on our home calculators page.
Before you dig
This is a materials estimate. Post depth, frost depth, fence height limits and permits are set by local code, so check them before you build. In the US, call 811 before you dig to have buried lines marked.
Fence calculator FAQ
How many posts do I need for a 100 ft fence?
With an 8 ft maximum spacing, 14 posts: 2 end posts and 12 line posts, set 7 ft 8-5/16 in apart on center.
How many rails does a fence need?
About one per 24 in of height. That's 2 rails a section on a 4 ft fence and 3 on a 6 ft fence.
How many pickets for 100 ft of fence?
With 5.5 in pickets and no gap, 219 before waste, or 230 with five percent added.
Do corner posts count twice?
No. Two runs that meet share one corner post.
Related tools
Bag yields match the concrete calculator's. To pick a waste allowance for cuts, see how much waste to add.