Case 1
- Fence length
- 30m
- Post spacing
- 2.5m
13posts
Open with these valuesFence Post Calculator
13posts
Result: 13 postsA straight fence needs one more post than it has sections: divide the length by the spacing, round up, add one. A 30 m run at 3 m spacing has 10 sections and 11 posts. That extra post is the classic fencepost error — it is the one that closes the far end of the run.
Worked examples
Case 2
- Fence length
- 20m
- Post spacing
- 2m
11posts
Open with these valuesCase 3
- Fence length
- 31m
- Post spacing
- 2.5m
14posts
Open with these valuesHow it's calculated
posts = ⌈length ÷ spacing⌉ + 1
- StepMeasure the straight run from the first post to the last, in metres.
- StepSet the spacing your panels call for — timber fences usually sit 2.4 to 3 m apart.
- StepDivide length by spacing and round up: that is the number of sections.
- ResultAdd one post to close the far end. Corners and gates need their own on top.
What this number means
A part-used section still needs its own post
31 m at 2.5 m spacing does not come out even: the run takes 13 sections, the last one short, and 14 posts. Dropping that remainder would leave the far end of the fence standing on nothing.
The answer is a count, so it moves in steps
Length and spacing are metres, but posts come in whole pieces. Stretching a 30 m run by a metre changes nothing at 2.5 m spacing, and the metre after that adds a post.
The n + 1 rule is quoted, the rounding is not
The source behind this calculator states that n sections need n + 1 posts and names the two other shapes: a closed loop takes n, a run wedged between two walls takes n − 1. Rounding a part section up to a whole one is trade practice the source does not cover.
One straight run at a time
The formula describes a single straight line of evenly spaced posts. Measure each straight segment between corners on its own, add a post for every corner and for every gate, then total them.
Commonly misread
30 m divided by 2.5 m spacing is 12, so I ordered 12 posts.
12 counts the sections, which are the gaps between posts. A free-standing run is closed by a post at each end, so 12 sections need 13 posts.
My fence closes into a rectangle, so I added the extra post.
A closed loop needs exactly as many posts as sections, because the last section comes back to the first post. The + 1 belongs to a run with two open ends.
I entered the whole boundary, corners included, as one length.
This calculator covers one straight run with even spacing. Split the boundary at the corners, run each segment through separately and add a post per corner.
Reference table
| Length, spacing | Sections | Posts |
|---|---|---|
| 0.1, 0.1 | 1 | 2 |
| 1, 2 | 1 | 2 |
| 20, 2 | 10 | 11 |
| 30, 2.5 | 12 | 13 |
| 30, 3 | 10 | 11 |
| 31, 2.5 | 13 | 14 |
Questions
How many fence posts do I need?
Divide the fence length by the post spacing and round up for the number of sections, then add one for the far end. A 30 m run at 2.5 m spacing needs 12 sections and 13 posts.
Why is there always one more post than sections?
Each section is the gap between two posts, so a straight run is bounded by a post at each end. With 12 sections you have 11 posts in between plus one at each end, 13 in total.
Does the count change for a loop or a wall-to-wall fence?
Yes. A fence that closes into a loop needs exactly as many posts as sections, and a run wedged between two walls with no end posts needs one fewer. This calculator assumes the usual case: a free-standing straight run with a post at each end.
What is a typical fence post spacing?
Timber and panel fences commonly sit about 2.4 to 3 m apart, matching standard panel widths, while wire and post-and-rail fences can run wider. Closer spacing makes a fence stiffer against wind but uses more posts.
Does this include gates and corners?
No. It covers a single straight run with evenly spaced posts. Add one post per corner and treat each straight segment between corners as its own run.
Sources and last check
Information, not professional advice.