Tool
Post, Rail and Picket Calculator
Enter the length of your fence run and the spacing you plan to use, and this tool returns the posts, rails and pickets to order. It counts both end posts, works out rails from the fence height, and calculates pickets from the width of the picket plus the gap you leave between them.
Use it to check a quote or a material list before you spend money. The numbers update as you type, so you can compare 8 foot and 6 foot post spacing, or a 6 foot fence against a 4 foot one, and see what each change costs you in material.
Posts needed
14
13 sections at 8 ft centers, both ends included
- Rails (3 per section)
- 39
- Pickets per section
- 16
- Pickets, whole run
- 208
- Picket coverage
- 96%
Corners, ends and gate posts are terminal posts and need bracing, so add one brace kit for each. Concrete is counted separately — about two 80 lb bags per post, or use the concrete calculator for your exact hole size.
How these counts are worked out
Posts are placed at the start of the run and every spacing interval after it, so a 100 foot run at 8 foot spacing gives 13 intervals and 14 posts. That extra post is the one people forget: the run has to end somewhere, and skipping it leaves a rail hanging in the air.
Rails run between posts, so the count is the number of sections multiplied by the rails per section — two for a 4 foot fence, three for a 5 or 6 foot fence. Pickets are counted per section from the picket width plus the gap: at 5½ inch pickets with a ¼ inch gap, a section holds 16 pickets, because 96 inches of section divided by 5.75 inches of coverage leaves no room for a seventeenth.
Rules of thumb worth knowing
- Post spacing: 8 feet standard for wood, 6 feet for tall fences, heavy gates and exposed sites, 10 feet for chain link line posts.
- Terminal posts at corners, ends and gate openings carry the load and need bracing or a thicker post than line posts.
- Concrete: about two 80 lb bags per post for a 9 inch hole 30 inches deep. The concrete calculator sizes it exactly.
- Dig below the frost line. In cold regions that means 36 to 42 inches rather than the 30 inches used in mild ones.
- Add a waste allowance of about 10 percent on pickets and rails. Boards split, and boards get cut wrong.
Common questions
- How many posts do I need for 100 feet of fence?
- At 8 foot post spacing, a 100 foot run needs 14 posts: 13 spaces plus one post at the far end. Posts are needed at both ends of every run, at every corner, and on each side of a gate, and those terminal posts need bracing, so a run with a gate and a corner ends up with a few more posts than the length alone suggests.
- What is the standard post spacing for a fence?
- 8 feet on center is the standard for wood privacy and picket fence, with 6 feet used for tall fences, heavy gates and windy areas. Chain link uses 10 foot line posts, and panel systems are set at the panel width, usually 6 or 8 feet, because the panels dictate the spacing.
- How many rails does a fence need?
- Two rails for a 4 foot fence and three rails for a 5 or 6 foot fence is the common standard. Taller fences, or fences carrying a heavy picket weight, get a fourth rail. The tool sets the count from the height you enter.