Fence Calculator - Posts, Rails, Pickets & Concrete

Fence Parts Quick Reference

Posts, rails, and pickets for common privacy-fence layouts at 8 ft post spacing, 6 ft fence height, 5.5 in pickets with 1/2 in gap. Use this for the lumberyard conversation.

Add gate posts (one extra heavy post per gate), corner posts, and 1-2 bags of concrete per post hole. For 3-rail fence (common in 6 ft tall), add 50% more rails. For 1x6 pickets at horizontal layout, the count changes - calculate by linear feet of fence x rows of horizontal.

How Fence Math Actually Works

Fence count is driven by three numbers: total length, post spacing, and picket module.

• Sections = ceil(total length / post spacing). At 100 ft long, 8 ft spacing: ceil(100/8) = 13 sections.
• Posts = sections + 1 + terminal posts (corners, gates). 13 sections needs 14 posts plus extras.
• Rails = sections x rails-per-section. Two-rail fence on 13 sections needs 26 rails.
• Pickets = total length / picket module. 5.5 in pickets + 1/2 in gap = 6 in module. 100 ft / 0.5 ft = 200 pickets. With 10% waste: 220.
• Post concrete = posts x (pi x post-hole-radius² x depth) / 27. 14 holes at 9 in dia x 30 in deep = 14 x 0.74 = 10.4 cu ft = 0.39 yd³ or about 16 of the 60 lb bags.

Post Setting - Where Fences Fail

Posts that move kill fences. The hole, depth, and concrete decide whether the fence stands for 20 years or falls in 3.

• Hole depth: 1/3 of post-above-ground height as a starting point. A 6 ft tall fence needs 24 in deep holes. In cold climates, go below frost depth (36-60 in) for gate and corner posts.
• Hole diameter: 3x post diameter. A 4 in post wants a 12 in hole.
• Gravel base: 4-6 in of gravel at the bottom for drainage. Posts that sit in water rot fast.
• Concrete: fast-set (QUIKRETE Quikrete Fast-Setting Concrete) is the standard for fence posts. Pour dry into the hole around the post, add water on top.
• Plumb and brace: use a level and braces for 24 hours until concrete sets.
• Soil-only setting (no concrete): works for low-height (under 4 ft) decorative fences. Tamp the soil hard. Will need re-tamping every few years.

Fence Types

Height and Code

Fence height limits vary by jurisdiction, lot location, and use.

• Front yard: 36-48 in maximum in most US suburbs. Higher requires variance.
• Backyard / side yard: 6 ft (1.8 m) is standard. Some jurisdictions allow 7 or 8 ft.
• Pool barriers: 48-60 in minimum, self-closing self-latching gate, code-mandated. ICC pool code or local equivalent.
• UK: permitted development up to 2 m back fence, 1 m for fences fronting a road. Higher needs planning permission.
• India: typical residential boundary 5-7 ft (1.5-2.1 m), no national height code - local municipal rules apply.
• Australia: NSW Dividing Fences Act caps shared fences at 1.8 m unless agreed otherwise; council may require lower in front.

Always check the local rule before ordering. A 7 ft fence in a 6 ft area gets a stop-work notice and a top-cut.

Gates

A gate is the most expensive linear foot of fence. Plan it specifically:

• Walk gate: 36-48 in wide. Heavier posts on both sides (6x6 or doubled 4x4).
• Drive gate: 10-16 ft wide, often a double gate. Posts must carry the load - 6x6 minimum.
• Hardware: two hinges and a latch minimum; for heavy or tall gates, three hinges plus a drop pin.
• Brace: diagonal brace from upper-latch corner to lower-hinge corner.
• Self-closing / self-latching: required by pool code in most US jurisdictions.

Cost Estimates Around The World

2026 retail prices for 6 ft tall residential privacy fence, installed.

Brand reference: US - CertainTeed Bufftech (vinyl), Trex Fence (composite), Cedar West, Master Halco (chain link); UK - Forest Garden, Grange, Jacksons Fencing; Australia - Colorbond, Stratco, Jasons Industries; India - Tata Wiron, Jindal Stainless. A two-person crew installs 50-100 lf of privacy fence per day on flat ground.

Common Mistakes

• Forgetting gate posts and terminal posts - they need beefier hardware and concrete.
• Setting posts too shallow - frost or wind heaves them within two seasons.
• Using untreated lumber below grade - rot in 5 years.
• Skipping concrete on tall or windy-site fences - posts lean.
• Wrong picket module - 5.5 in pickets + 1/4 in gap is 5.75 in, not 6 in. Affects total count.
• Tight pickets (no gap) - wood expands in humid weather and the fence cups.
• Not pulling string lines before setting posts - the fence ends up wavy.
• Skipping the gravel base in the post hole - water sits, the post rots from the bottom up.

Related Construction Calculators

For wire mesh chain link or field fence, see the Fence Mesh Calculator. For concrete in post holes, use the Concrete Calculator. For lumber from board-foot perspective, see the Lumber Calculator. For brick or stone boundary walls, switch to the Brick Calculator or Block Calculator. More tools live on the Construction Calculators hub.