Fence Calculator

How many fence posts and pickets do I need? Divide run length by post spacing for sections, add one post (posts = sections + 1), then size pickets from run × 12 ÷ (picket width + gap). A 100 ft run with 5.5″ pickets, 1″ gaps, 2 rails, and 8 ft spacing needs 13 sections, 14 posts, 185 pickets, 26 rails, and about 14 bags of concrete.

Reviewed / updated August 2026

Full walkthrough: How to Estimate Materials for Any Home Project

Your inputs

ft

Straight-line fence length (add segments for corners)

in

Common dog-ear pickets are about 5.5″

in

Many privacy fences use 2 or 3 rails

ft

Default 8 ft on center

Result

Fence materials

14 posts

185 pickets · 26 rails · 13 sections

Sections
13
Posts
14
Pickets
185
Rails
26
Concrete bags (~50 lb)
14

A 100 ft run at your spacing needs 13 sections, 14 posts, 185 pickets, and 26 rails. Plan about 14 bags of concrete (1 per post).

What-if: 5.5″ vs 3.5″ pickets (same run)

PicketPicketsPostsRails
5.5″1851426
3.5″2671426

Suggested next step

Add posts manually for gates and outside corners — this model uses one post per spacing along a straight run.

How the fence calculation works

Plan a straight privacy or picket fence from run length, post spacing, and picket + gap width:

  1. Sections = ceil(run ft ÷ post spacing ft)
  2. Posts = sections + 1 (add more for gates/corners)
  3. Pickets = ceil(run ft × 12 ÷ (picket width + gap))
  4. Rails = sections × rails per section
  5. Concrete bags = posts when the toggle is on (≈1 × 50 lb bag each)

Results update live. Compare 5.5″ vs 3.5″ pickets on the same run. For board-foot framing lumber see the Lumber Calculator; for post footings volume see the Concrete Calculator. More DIY tools live on the Home Improvement hub.

Source note: Post +1 and picket spacing formulas are standard fence takeoff rules of thumb; concrete per post varies by soil and hole size. Updated August 2026.

Worked example

100 ft run, 5.5″ pickets, 1″ gap, 2 rails per section, 8 ft post spacing, concrete on:

  1. Sections = ceil(100 ÷ 8) = 13
  2. Posts = 13 + 1 = 14
  3. Pickets = ceil(1,200 ÷ 6.5) = 185
  4. Rails = 13 × 2 = 26
  5. Concrete ≈ 14 bags

Those are the default inputs. Narrower pickets raise the picket count without changing posts or rails if spacing stays the same.

Methodology and notes

This model is a straight-line takeoff. Corner lots need an extra post at each turn; slopes may shorten rail lengths. Always check HOA and code setbacks before digging post holes.

Frequently asked questions

How many posts for a 100 ft fence?

At 8 ft spacing: sections = ceil(100 ÷ 8) = 13, posts = 13 + 1 = 14 for a straight run. Add posts for gates and each outside corner.

How do you calculate fence pickets?

Pickets = ceil(run feet × 12 ÷ (picket width inches + gap inches)). Example: 100 × 12 ÷ (5.5 + 1) ≈ 184.6 → 185 pickets.

How much concrete per fence post?

A common DIY planning rule is one 50 lb bag per post for typical holes. Soft soil, large diameter holes, or frost-line depth can take more — adjust after you dig.

What picket width should I use?

Many privacy pickets are about 5.5″ wide with a ½–1″ gap. Narrower 3.5″ stock needs more pieces for the same run — compare in the what-if table.

Does this include a gate?

No. Gate openings reduce picket count and usually need extra posts and hardware. Subtract the gate width from the picket run and add posts at each gate jamb.

Related tools

Related calculators — live tools and upcoming pages for internal linking.