Fence Calculator
Count the posts, rails and pickets a run of fence needs.
Last reviewed September 19, 2026
Result
Buy 14 postsEstimate
No allowance is added. Posts and rails are cut to fit and rarely wasted, but pickets are the piece that gets miscut, so buying a few spare is normal. The picket count also assumes the run divides evenly; the last section usually needs one ripped narrower.
- Sections
- 13
- Rails
- 26
- Pickets
- 209Estimate
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Results are estimates for planning only. Actual needs vary with site conditions, products and workmanship. Always confirm quantities with your supplier and follow local building codes and manufacturer instructions. Read the full disclaimer
How to use it
- Measure the total length of the fence run.
- Set the post spacing. Eight feet, or 2.4 m, is the usual maximum for timber.
- Choose two or three rails per section, and enter the actual picket width and the gap you want.
- Add one post for each corner, and two for each gate.
- Read the post, rail and picket counts.
How it is calculated
A fence is four separate counts off one measurement:
sections = ceil(length ÷ spacing)
posts = sections + 1 + extra posts
rails = sections × rails per section
pickets = ceil(length ÷ (picket width + gap))The post count is the one people get wrong. A run of fence has one more post than it has sections, because the two end posts are not shared with anything. Thirteen sections need fourteen posts.
Pickets are counted from the pitch, which is the picket width plus one gap, not the picket width alone. At 5.5 in wide with a 0.25 in gap each picket occupies 5.75 in of run, so 100 ft takes 209 rather than the 219 you would get from the width alone.
Practical tips
Measure the run, not the property line. Fences are usually set back from the boundary, and a run that follows a slope is longer than its plan measurement. Measure along the ground where the fence will actually stand.
Set the end and corner posts first. String a line between them and set the intermediate posts to that line. Working from one end and hoping it comes out straight almost never does.
Buy the pickets last. Once the posts and rails are up you can measure the real spacing between them and adjust the gap slightly so the last picket in each section comes out full width, which looks much better than a narrow sliver.
Use the actual widths, not the nominal ones. A nominal 1×6 picket measures 5.5 in. Using 6 in in the calculation undercounts by nearly a tenth, which is nineteen pickets on a 100 ft run.
Check before you dig. Call the utility locating service, and check whether your fence needs a permit or has a height limit. Both are common and both are cheaper to find out about before the posts are in concrete.
With your numbers
- Sections = 100 ft ÷ 8 ft spacing, rounded up to 13
- Rails = 13 sections × 2 = 26
- Pickets = 100 ft ÷ (5.5 in + 0.25 in) = 209
- Posts = 13 sections + 1 end post + 0 extra = 14
Quick reference
No allowance is added. Posts and rails are cut to fit and rarely wasted, but pickets are the piece that gets miscut, so buying a few spare is normal. The picket count also assumes the run divides evenly; the last section usually needs one ripped narrower.
| Job | Posts to buy |
|---|---|
| 50 ft, 8 ft spacing | 8 |
| 100 ft, 8 ft spacing | 14 |
| 150 ft, 8 ft spacing | 20 |
| 100 ft, 6 ft spacing, 3 rails | 18 |
| 100 ft privacy, no gap | 14 |
| 30 m, 2.4 m spacing | 14 |
| 50 m, 2.4 m spacing | 22 |
Common questions
- How many posts do I need for a 100 foot fence?
- Fourteen, at 8 ft spacing: the run divides into 13 sections and a straight run needs one more post than it has sections. Add one for each corner and two for each gate on top of that.
- How far apart should fence posts be?
- Six to eight feet, or 1.8 to 2.4 m, for a timber fence. Eight feet is the common maximum because standard rails come in 8 ft lengths. Closer spacing is stiffer and matters more on exposed sites and for tall privacy fences, which catch a lot of wind.
- Why is it one more post than sections?
- Each section needs a post at both ends, and neighbouring sections share one. A straight run of 13 sections has 14 posts. A fence that closes on itself, like a full enclosure, needs one fewer because the last section shares the first post.
- What gap should I leave between pickets?
- A quarter inch, or about 6 mm, is typical for a picket fence and leaves room for the timber to swell when wet. For a solid privacy fence set the gap to zero, though green timber laid tight will shrink and open up gaps as it dries.
- Do I need to account for the last picket not fitting?
- Yes. The count divides the run by the picket pitch and rounds up, so the last picket in each run usually needs ripping narrower. That is normal and it is why the count is a minimum rather than an exact order.
- How deep should the posts go?
- A common rule is a third of the post's above-ground height, or 2 ft for a 6 ft fence, whichever is deeper, and below the frost line where ground freezes. Depth requirements vary locally, so check before you dig.