Calculators

Fence Calculator

Posts, rails, pickets or panels and bags of post concrete for a wood fence, including gates.

How it works

Take the gate openings out of the fence length and divide what is left by the post spacing to get the sections, rounding up. There is one post per section plus one to finish the run, and each gate adds a post because the opening breaks the line. Rails are sections × rails per section. Pickets are the run in inches divided by one picket plus its gap. Concrete fills each hole around the post.

posts = ⌈(length − gates) ÷ spacing⌉ + 1 + gates; pickets = run × 12 ÷ (picket + gap)
Spacing
6–8 ft between post centres; 8 ft suits 8 ft rails
Rails
2 for fences up to 4 ft, 3 for 5–6 ft
Picket
A 1 × 6 is 5½ in wide; a 1 × 4 is 3½ in

Worked example

A 100 ft, 6 ft privacy fence with one 4 ft gate, posts 8 ft apart, three rails, 1 × 6 pickets with no gap.

  1. 1Picket run: 100 − 4 = 96 ft
  2. 2Sections: 96 ÷ 8 = 12; posts: 12 + 1 + 1 = 14
  3. 3Rails: 12 × 3 = 36
  4. 4Pickets: 96 × 12 ÷ 5.5 = 209.5, so 210
  5. 5Concrete: 8 ft posts set 2 ft deep take about 2 bags of 50 lb mix each

14 posts, 36 rails, 210 pickets and 29 bags of fast-setting concrete, plus the gate hardware.

Frequently asked questions

How far apart should fence posts be?

Usually 8 ft apart for a wood fence, which lets 8 ft rails span from post to post. In windy areas, for tall privacy fences or with heavy panels, 6 ft is stronger. Vinyl and metal panels come in fixed widths, so match the spacing to the panel.

How deep should fence posts be set?

About a third of the post's length, and at least 2 ft: a 6 ft fence on 8 ft posts sets them 2 ft deep. Where the ground freezes, go below the frost line so frost heave does not lift them. Put a few inches of gravel in the bottom of each hole for drainage.

How many bags of concrete per fence post?

About two 50 lb bags for a 4 × 4 post in a 10 in hole 2 ft deep with gravel in the bottom, and more for deeper holes or 6 × 6 posts. The concrete bag calculator works out any hole size.

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