Wood & Trim
Fence Post Calculator
Lay out fence posts at even spacing along an open run or a closed perimeter.
Enter your measurements
Results update as you type.
About this calculator
Enter the fence length (or perimeter) and the maximum post spacing. The tool picks the smallest whole number of bays so spacing never exceeds your maximum, then reports the exact even spacing and post count. A closed loop needs no extra end post; an open run does.
How to use this calculator
- Measure the fence run or perimeter.
- Enter the maximum spacing your fence design allows.
- Choose open run or closed loop.
- Calculate; mark posts at multiples of the even spacing.
Formula
Bays = ⌈length ÷ max spacing⌉
Even spacing = length ÷ bays
Posts = bays + 1 (open run) or bays (closed loop)
Assumptions
- Spacing is even and never exceeds your maximum — the bay count rounds up, not the spacing.
- A closed loop shares its start and end post, so it needs one fewer post.
- Positions are measured from one end of the run.
Common mistakes
- Using an open-run post count for a closed loop.
- Omitting separate gate and corner requirements.
- Treating bay spacing as a structural wind-load design.
Worked example
Try it: press “Load example” above the form.
30 m at 2.5 m max is exactly 12 bays; an open run needs 13 posts at 2.5 m spacing.
Limitations
No post depth, footing or structural advice.
Frequently asked questions
Why does an open fence need one extra post?
An open run with n bays needs n + 1 posts. A closed loop can share its starting and ending post. Choose the topology matching the actual layout.
Are gate posts included?
Only the stated simple run is counted. Gate openings, double posts, corners and different support requirements need their own schedule.
What does the worked example show?
30 m at 2.5 m max is exactly 12 bays; an open run needs 13 posts at 2.5 m spacing.
Which assumptions should I check before using the result?
No post depth, footing or structural advice.
Sources
Sources explain the methods and any named product presets. Check your product label where coverage, yield or density differs.
Calculation documentation · Updated 2026-11-08 · Version 1.6.4. Estimates are planning aids. Confirm quantities, coverage and prices with your supplier before purchasing. Found an error? Report it.
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