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Fence Calculator

A fence calculator works out everything a fence run needs in one shot — posts, rails, pickets and the bags of concrete to set the posts — from the fence length, your post spacing and the picket width. No more three separate guesses at the store.

Your measurements

Result

Pickets are where people miss: the count depends on the picket width plus any gap between boards, not just the length. Set those and this nails the board count, including the extra post to close the run.

How it is calculated

Sections = length ÷ post spacing (rounded up); posts = sections + 1. Rails = sections × rails-per-section. Pickets = length × 12 ÷ (picket width + gap). Concrete = posts × bags-per-post. Board-on-board or shadowbox styles overlap pickets and need roughly double the picket count.

Steps

Enter the total fence length.
Set the post spacing (8 ft is typical for wood).
Choose 2 or 3 rails per section by fence height.
Enter the picket width and any gap between pickets.
Read posts, rails, pickets and concrete bags.

Worked example

A 100 ft fence at 8 ft spacing needs 14 posts and 13 sections; with 5.5 in pickets butted tight, about 219 pickets.

Common questions

How many fence posts do I need?

Length ÷ post spacing, plus one to finish the run. At 8 ft spacing, a 100 ft fence needs 14 posts.

How many pickets for a fence?

Fence length (in inches) ÷ (picket width + gap). The calculator does it — tighten the gap to zero for a privacy fence.

How many bags of concrete per fence post?

Usually 1-2 bags of fast-setting mix for a standard 4×4 post; heavier or taller posts need more. Set the per-post figure to match your hole size.

How many rails per section?

Two for fences up to about 5 ft, three for 6 ft and taller to keep pickets from warping.