Enter total fence length and post spacing to get posts, pickets, rails, and concrete bags.
A 100-linear-foot privacy fence with 6-foot post spacing requires 18 posts, 209 pickets (1×6 boards), 3 rails per bay, and approximately 18 bags of concrete. Our calculator uses the correct 2.09 pickets-per-linear-foot formula for 1×6 boards with standard 1/2-inch spacing — one of the most common sources of significant estimation errors in fencing projects.
Fencing is one of the most frequently underestimated projects in home construction. The most common mistake: calculating picket quantity based on the nominal board width (6 inches) instead of the actual board width (5.5 inches) plus the spacing gap. Using the wrong formula consistently results in 10–15% too few pickets, requiring a second supply run mid-project.
Standard fence post spacing is 6–8 feet on-center. Eight-foot spacing is the maximum recommended for a standard 6-foot privacy fence with 2×4 rails — beyond 8 feet, rails flex noticeably and the fence lacks rigidity. Six-foot spacing is stronger and preferable in high-wind areas or for fences over 6 feet tall. To calculate post count: divide total fence length by post spacing and add 1 for the end post. A 100-foot fence at 8-foot spacing = 100 ÷ 8 = 12.5, round up to 13 bays + 1 post = 14 posts. For corners, gates, and line ends, add additional posts as needed.
A nominal 1×6 fence board is actually 5.5 inches wide. With a standard 1/2-inch gap between boards for drainage and thermal expansion, each board occupies 6 inches of fence width. The industry-standard formula accounts for post widths (typically 3.5 inches for a 4×4 post) and other variables, resulting in approximately 2.09 pickets per linear foot of fence. Our calculator uses this formula precisely. The simpler (and incorrect) 2.0 pickets/foot formula for a 100-foot fence understates quantity by approximately 9 pickets — a meaningful shortage on a large project.
Posts must be set below the frost line to prevent heaving in cold climates. The minimum post depth is the local frost depth plus 6 inches of gravel drainage at the bottom of the hole. In North America, where the frost line is 48–60 inches, posts for a 6-foot fence should be set 5–6 feet deep, leaving 6 feet above grade (post total length: 11–12 feet). A practical rule of thumb: bury 1/3 of the total post length for fences under 6 feet; bury up to 40% for taller or high-wind applications. Each post hole requires approximately 1 bag of fast-setting concrete (50 lb), yielding about 0.375 cubic feet — sufficient for a 10-inch diameter hole 2.5 feet deep.
A standard 6-foot privacy fence uses 3 horizontal rails: one at 6 inches from the top, one at 6 inches from the bottom (code in many areas requires the bottom rail to be at least 2 inches above grade), and one in the middle at 3 feet. Rails are typically 2×4 lumber. Total rail length = number of bays × bay width × number of rails. For a 100-foot fence at 8-foot spacing (12.5 bays) with 3 rails: 12.5 × 8 × 3 = 300 linear feet of 2×4. Purchase 2×4×8 boards for standard 8-foot bays with no cutting waste.
Gates are the most vulnerable part of any fence and the most common point of failure. Key rules: use 4×4 minimum gate posts, preferably 4×6 for double gates. Set gate posts at least 6 inches deeper than line posts to resist the leverage of a swinging gate. Use heavy-duty strap hinges rated for the gate weight. Every gate needs a latch, a stop (to prevent swinging past 90°), and a diagonal brace (running from the latch bottom corner to the hinge top corner) to prevent sag.
At 8-foot post spacing: 100 ÷ 8 = 12.5, rounded up to 13 spaces + 1 end post = 14 posts. For corners and gates, add additional posts. Our calculator accounts for your specific fence layout including corners and gate openings.
The standard rule is 1/3 of the total post length below grade. For a 6-foot fence using 9-foot posts: bury 3 feet. In cold climates, add the frost depth: if the frost line is 4 feet, bury at least 4.5 feet. In North America, a 6-foot fence typically requires 10.5–11-foot posts.
Cedar and redwood are the premium choices — both have natural rot and insect resistance and stay attractive for decades. Pressure-treated pine is the economical standard: UC4B for posts (ground contact), UC3B for rails and pickets. Untreated spruce or pine is not recommended for outdoor fencing — they deteriorate quickly in contact with moisture.
Ground anchor systems (post spikes or drive anchors) are available for above-ground installation. They're faster but not appropriate for frost climates — the post will heave and the fence will misalign over a few seasons. In non-frost climates, high-quality post anchors driven to the correct depth are a practical option for lighter fences.
A properly built cedar or redwood fence lasts 20–30+ years with periodic sealing. A pressure-treated pine fence lasts 15–25 years. Key longevity factors: post quality (UC4B treatment), proper post depth below frost line, and a quality exterior stain or sealer applied every 3–5 years. The post is almost always the first component to fail.
Common questions answered — straight from the job site.
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