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Wood Fence Calculator Guide
Building a wood fence means buying the right number of posts, rails, and pickets before you start. This wood fence calculator works out every part from your fence length, height, and picket spacing.
Posts = sections + 1. Pickets = fence length in inches ÷ (picket width + gap). Rails run between posts — two for fences up to 5 ft, three for 6 ft and taller.
How Many Pickets Do I Need?
Divide the total fence length in inches by the picket width plus the gap. A 100-foot fence using 5.5-inch pickets with a 3/8-inch gap needs about 205 pickets. Tighter gaps and narrower pickets both raise the count.
Posts, Spacing, and Rails
Posts are normally set 6 or 8 feet apart. Eight feet is standard and cheaper; six feet is stronger and better in high wind. Remember you always need one more post than sections — a 100-foot fence with 8-foot spacing has 13 sections and 14 posts.
Rails are the horizontal boards the pickets attach to. Fences 5 feet and under use two rails; 6-foot and taller fences use three so the pickets don't warp or bow over time.
Don't Forget the Concrete
Each post needs concrete. This calculator estimates bags based on a hole about three times the post width and a depth of one-third the fence height. Check our fence post depth calculator for exact hole depths, especially if you're in a frost-prone area.
These are estimates for planning and budgeting. Always confirm quantities against your actual site measurements and check local building codes and permit requirements before you buy or build.
Related: Fence Post Depth, Privacy Fence Calculator, and Vinyl Fence Calculator.
Frequently Asked Questions
How many pickets do I need for a fence?
Divide the fence length in inches by the picket width plus the gap. A 100-foot fence with 5.5-inch pickets and a 3/8-inch gap needs roughly 205 pickets.
How far apart should fence posts be?
Six to eight feet apart is standard. Eight feet is the common choice, while six feet gives a stronger fence in windy areas or on slopes.
How many rails does a fence need?
Use two rails for fences up to 5 feet tall and three rails for 6-foot and taller fences to keep pickets straight over time.
How many posts for a 100-foot fence?
With 8-foot spacing you need 13 sections and 14 posts, since a fence always needs one more post than it has sections.
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