Fence Calculator
Estimate posts, rails, and pickets for a wood fence.
Post count assumes a straight run; add one post for each corner or gate. Set gap to 0 for privacy fences.
A fence is really three shopping lists in one — posts, rails, and pickets — and each follows its own math. Get one wrong and you’re either driving back to the lumberyard mid-project or storing extra lumber for years. Our fence calculator above works out all three from your fence length, post spacing, and picket dimensions.
The Three Calculations
Posts = (Fence length ÷ Post spacing), rounded up, + 1 A 100 ft run with 8 ft spacing needs 13 sections’ worth of posts — 14 posts total, because a run of N sections always needs N+1 posts.
Rails = Sections × Rails per section Sections = posts − 1. Two rails per section is standard for fences up to 5 ft; use three for 6 ft privacy fences to prevent sagging and cupping.
Pickets = Fence length (in inches) ÷ (Picket width + Gap) For a solid privacy fence, set the gap to 0. For spaced picket styles, a common gap is 1.5–2.5 inches.
Add one post for every corner, gate side, and direction change — the calculator assumes a straight run.
Choosing Post Spacing
8 feet is the workhorse spacing: fewer posts, fewer holes, lower cost. Works with standard 8 ft rails with no cutting.
6 feet makes a noticeably stiffer fence and is the better choice in high-wind areas, on slopes, and for heavy privacy panels that catch wind like a sail. Pre-built panels come in both sizes — match your spacing to the panels before digging anything.
Don’t Forget the Below-Ground Math
Posts need to be long enough to stand in the ground and still reach the top of the fence. The rule: bury one-third of the post height, minimum 2 feet, and get below your local frost line. A 6 ft privacy fence needs 8 ft posts set in holes about 30–36 inches deep.
Concrete per post: a 10-inch-diameter hole 30 inches deep takes roughly 1.5–2 bags of 50 lb fast-setting concrete. Multiply by your post count — concrete is the most commonly under-bought fence material. (Our concrete calculator can help with larger footings.)
Material Choices at a Glance
Pressure-treated pine — the budget standard; lasts 15–20 years if kept sealed. Let it dry a few months before staining.
Cedar — naturally rot-resistant, looks better, costs more. Posts still benefit from pressure-treated wood below grade.
Vinyl — no painting, no rot, higher upfront cost; sold as panel systems, so buy by section count.
Metal posts with wood panels — increasingly popular hybrid: steel posts outlast wood in the ground while the fence face stays warm-looking.
Before You Dig
- Call 811 (in the US) a few days before digging — free utility marking is required and could save your life.
- Confirm the property line. Building a fence even inches over the line is an expensive dispute. When in doubt, pay for a survey stake-out.
- Check HOA and local codes: height limits (often 6 ft back yard, 4 ft front), “good side out” rules, and permit requirements are common.
- Plan gates separately: each gate needs its own hardware, hinge-side post (often a heavier 6×6), and typically 4×4 framing.
Frequently Asked Questions
How many pickets for 100 feet of solid privacy fence? With 5.5-inch pickets and no gap: 1,200 ÷ 5.5 ≈ 219 pickets. Add ~5% for splits and culls — cheap insurance at picket prices.
How many posts for 200 feet of fence? At 8 ft spacing: 26 posts for a straight run, plus one for each corner or gate.
Should pickets touch the ground? No — leave at least 2 inches of clearance. Ground contact wicks moisture and rots pickets from the bottom years early. A gravel strip under the fence line buys even more life.
Estimates are for planning purposes. Check local codes for post depth, height limits, and permits before building.
Notes from building this calculator
The post count is where fence estimates usually go wrong, and it is an off-by-one problem. A 100-foot run at 8-foot spacing needs 13 posts, not 12, because a run of n sections carries n+1 posts. We solve for sections first and then add the terminal post. Gates are counted separately, since gate posts are normally upsized and set deeper than line posts.
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Sources and Further Reading
Coverage figures and material constants are cross-checked against manufacturer technical data sheets before publication. Assembly and dimensional references come from applicable model building codes. See our Methodology page for how figures are selected and verified.
Planning estimate only. Results assume standard conditions and are intended for material planning. Verify against your product’s technical data sheet and your local building code before purchasing. Structural, electrical, and gas work should be specified by a licensed professional.
Last updated: August 7, 2026