How this calculation works
An open run needs one more post than its number of spans. Rounding the spans up keeps spacing at or below the entered maximum. A zero-length run returns one location by convention.
Posts = ceiling(length ÷ maximum spacing) + 1A worked example
A 20 m open run with at most 3 m spacing needs 7 spans and 8 posts.
Good to know
Assumes one straight run with posts at both ends. Corners, gates, shared posts, closed loops and structural requirements need separate treatment.
An open line has one more post than spans
Seven spans need eight boundary posts because neighboring spans share their intermediate posts. The two ends each need their own endpoint. For 20 m with a 3 m maximum spacing, rounding up gives seven spans and eight posts.
A closed loop follows a different counting pattern because the final span returns to the first post. This tool deliberately models one straight open run rather than treating every layout as interchangeable.
Corners and gates change the layout
Multiple runs can share corner posts, while gates may require additional or differently specified supports. Adding separate straight-run totals can double-count a shared corner. Sketch the actual layout before combining counts.
The tool calculates positions only. It does not specify post strength, footing depth, wind loading or material suitability. Those requirements depend on the fence system and site.
A few questions, answered
Does the count include both end posts?
Yes. The open-run formula includes a post at each end.
Can I use this directly for a closed boundary?
No. A closed loop shares its starting and ending post and needs a layout-specific count.