Fence Calculator

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.