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Units

Picket Fence Calculator

Get every picket, rail and post for your fence, plus the exact picket spacing that gives equal gaps between two posts.

New cedar privacy fence and gate along a backyard lawn
Units
Measure by
ft
corners

Where the fence turns.

Gates
4 ft gate
Picket fence details
ft
ft

Center to center, at most.

Picket width
in
Post size
in

Follows the height. Go deeper if your frost line is lower.

Hole diameter: 10.5 in, three times the post width.

Enter a fence length, draw the line on the map, or add sides to see your materials.

Picket spacing: an even gap that ends cleanly

Measure the space you want to fill, pick your picket and the gap you are aiming for. You get the number of pickets and the exact gap that makes every space the same, so you never end a bay with a sliver.

Layout
in

Inside face to inside face. 4x4 posts at 7 ft 10 in centers leave 90 1/2 in.

in
in

2 1/2 in is typical for a picket fence.

Pickets for an even gap

15pickets

Set every gap to 2 3/8 in, including the gap at each post (16 gaps).
Exact gap
2.375in
With 14 pickets
2 3/4in
With 16 pickets
2in
2 3/8 in
The bay to scale: 15 pickets, every gap the same.

Cut a spacer block to 2 3/8 in and use it between every picket. Fix the first picket one gap (2 3/8 in) from the post and check with a level every few pickets.

Around a pool

A 2 3/8 in gap passes the CPSC 4 in sphere rule. But when the horizontal rails are less than 45 in apart, as on most 4 ft picket fences, CPSC limits the gap to 1 3/4 in and puts the rails on the pool side. The barrier should also be at least 48 in high. Local codes can be stricter.

Pickets per 8 ft section

Counted the same way as the material list: along the rails from one post center to the next, rounded up to whole pickets.

Gap1x4 pickets1x6 pickets
1 1/2 in2014
1 3/4 in1914
2 in1814
2 1/2 intypical1713
3 in1612
3 1/2 in1512

1x4 pickets are 3 1/2 in (89 mm) wide and 1x6 pickets 5 1/2 in (140 mm). Add 10% for waste when you buy.

How the picket fence calculator counts

A picket fence is posts, rails and pickets with a gap between each picket. The calculator first splits your fence line into sections no longer than your post spacing, with a post at every corner, end and gate. Then it counts pickets section by section, because each picket takes up its own width plus one gap.

Pickets per section = (section length + gap) ÷ (picket width + gap), rounded up

Adding one gap to the section length accounts for the last picket, which needs no gap after it. Rails follow the height: two per section up to 4 ft, three up to 6 ft. The total gets 10% extra for pickets, rails and nails, the allowance Inch Calculator recommends for cutoffs and waste.

The spacing tool below the calculator answers a different question: how to lay out one bay so every gap is the same. With a gap at each post, a bay holds n pickets and n + 1 gaps.

Gap = (space between posts − pickets × picket width) ÷ (pickets + 1)

It tries the picket counts either side of your target and keeps the one whose gap comes closest.

A worked example

The calculator opens on 150 ft of 4 ft picket fence with two corners and one 4 ft walk gate. That makes three 50 ft sides. The gate splits one side into two 23 ft stretches, leaving 146 ft of fence.

  • Posts at 8 ft at most: each 23 ft stretch becomes 3 sections of about 7.67 ft, and each 50 ft side becomes 7 sections of about 7.14 ft. That is 20 sections and 22 posts (16 line, 2 corner, 2 end, 2 gate).
  • 1x4 pickets are 3 1/2 in wide. With a 2 1/2 in gap, a 7.67 ft section (92 in) takes (92 + 2.5) ÷ 6 = 15.75, so 16 pickets. A 7.14 ft section takes 15.
  • 6 × 16 + 14 × 15 = 306 pickets, plus 10% gives 337 pickets.
  • Two rails per section is 40 rails, or 44 with waste.
  • Holes 30 in deep take 61 bags of 50 lb fast-setting concrete, about 2.8 per post, and 6 ft posts.

For the spacing tool, take posts at 7 ft 10 in centers, the spacing America's Fence Store uses. With 4x4 posts that leaves 90 1/2 in between them. Aiming for 2 1/2 in gaps with 1x4 pickets:

  • (90.5 − 2.5) ÷ (3.5 + 2.5) = 14.7, so try 14 and 15 pickets.
  • 15 pickets use 52 1/2 in, which leaves 38 in for 16 gaps: 2 3/8 in each.
  • 14 pickets would leave 2 3/4 in gaps, and 16 would leave 2 in. 2 3/8 in is closest to the target.

How wide should the gap between pickets be?

America's Fence Store says a picket fence "generally has a 2 1/2" gap between the pickets", and that is the default here. Wider gaps use fewer pickets but let more through. The table under the calculator shows how the count per 8 ft section changes: 17 1x4 pickets at 2 1/2 in, 20 at 1 1/2 in, 15 at 3 1/2 in.

Nominal sizes are not actual sizes: ProWood lists a 1x4 as 3/4 by 3 1/2 in and a 1x6 as 3/4 by 5 1/2 in. Measure a picket from your store before you cut a spacer.

Picket fence gap rules around a pool

If the fence is part of a pool barrier, the gap is set by safety, not looks. The U.S. Consumer Product Safety Commission's pool barrier guidelines say:

  • The barrier should be at least 48 in high, and some places require 60 in.
  • No opening should let a 4 in sphere pass through.
  • If the horizontal rails are less than 45 in apart, the rails go on the pool side and the gap between pickets should be no more than 1 3/4 in.
  • The gap under the fence should be no more than 4 in, or 2 in over grass or pebbles.

A 4 ft picket fence with rails near the top and bottom has them less than 45 in apart, so the 1 3/4 in limit applies. At 1 3/4 in a 1x4 fence takes 19 pickets per 8 ft section instead of 17. Your local code may be stricter than CPSC, so check it before you build.

How many rails and nails does a picket fence need?

America's Fence Store uses two rails per bay for 4 ft fencing and three for 6 ft. Each picket gets two 6d nails at each rail. On a two-rail fence that is four nails per picket, and each rail end gets two 16d nails. Rails usually come as 8 ft 2x4s, so a section up to 8 ft needs one per row.

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