Fence Posts CalculatorFree online other calculator — instant results, no sign-up
Count posts on one straight open fence run at a maximum spacing.
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About the Fence Posts Calculator
The Fence Posts Calculator counts the posts needed for one straight, open fence run while keeping every gap at or below your chosen maximum spacing. It includes a post at each end of the run. With a fence length of 30 m and maximum post spacing of 2.4 m, the result is 14 posts.
- Fence length (m)
- The length of the straight fence run between its end posts, measured in metres, with a default of 30 m.
- Maximum post spacing (m)
- The largest permitted distance between adjacent post centres, measured in metres, with a default of 2.4 m.
Formula and method
B = ceil(L / S); P = B + 1. With the default inputs: B = ceil(30 / 2.4) = ceil(12.5) = 13; P = 13 + 1 = 14 posts.
- LFence run length in metres, measured between the centres of the end posts.
- SMaximum allowed post spacing in metres.
- BNumber of gaps, or bays, between posts.
- PTotal number of posts, including both end posts.
- ceilThe ceiling function, which rounds a value up to the nearest whole number.
Divide the fence length by the maximum post spacing, then round up to get a whole number of bays. Add one post because an open run needs a post at both ends. For 30 m divided by 2.4 m, the quotient is 12.5, so the run needs 13 bays and 14 posts. If those bays are evenly spaced, each is approximately 2.31 m long, below the 2.4 m maximum.
Worked example
These are the calculator's starting values and the results it actually produces for them.
Inputs
- Fence length30 m
- Maximum post spacing2.4 m
Results
- Result14 posts
How to use the Fence Posts Calculator
- 1Measure the straight run between the intended centres of its two end posts.
- 2Enter that measurement in Fence length (m); the default is 30.
- 3Enter the permitted maximum centre-to-centre distance in Maximum post spacing (m); the default is 2.4.
- 4Calculate the result: the default inputs produce 14 posts, including both end posts.
- 5Plan the post positions so that no bay exceeds the maximum spacing, and check the layout against your fence system's requirements.
Reading your result
The result row gives the total number of posts for the run, not the number of gaps or only the intermediate posts. The default result of 14 posts means two end posts and 12 intermediate posts, forming 13 bays. It is a layout count, not necessarily the number of new posts to purchase if suitable end posts already exist.
Limitations
This calculation assumes a single straight, open run with positive length and positive maximum spacing. It does not account for corners, gates, closed loops, shared posts between runs, slopes, fixed-width panels, or extra structural supports. Spacing is treated as centre-to-centre rather than clear space between post faces. The tool counts posts but does not establish a safe spacing, post size, foundation depth, or compliance with local requirements; choose those using the fence manufacturer's guidance and applicable building rules.
Common questions
Why does a 30 m fence at a maximum spacing of 2.4 m need 14 posts?+
Dividing 30 by 2.4 gives 12.5 bays. Rounding up gives 13 bays so the maximum spacing is not exceeded, and an open run with 13 bays needs 14 posts.
Do all the posts have to be exactly 2.4 m apart?+
No. The 2.4 m input is a maximum, not a required spacing. For the default 30 m run, distributing the 13 bays evenly gives a spacing of approximately 2.31 m.
Are the end posts included in the result?+
Yes, both end posts are included. If suitable posts already exist at both ends, the default layout still uses 14 posts in total, but only the 12 intermediate posts would need to be added.
Can I use this count for a fence with a gate or corners?+
Not without adjusting the layout. Gates and corners create required post locations and may need special supports; calculate each uninterrupted straight run separately and avoid counting shared posts twice.
Does the calculator save my information?+
Calculations run in your browser. While signed in, inputs and results are automatically recorded in account history; saving a result creates a separate saved record.
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Results are estimates for informational purposes and are not financial, medical or legal advice.