Start with the straight-run sections
The calculator converts the total length to feet, subtracts gate openings, and divides the remaining run by the selected post spacing. It rounds that result up to create the straight-run section count.
straight-run sections = ceil(net fence run ÷ post spacing)
Those sections are the part of the single run that receives rails. A gate opening is not counted as a fence section.
Use the height-based rail planning rule
The calculator converts the selected fence height to inches, divides it by 24, and rounds up. It always uses at least one rail per section.
rails per section = max(1, ceil(fence height in inches ÷ 24))
The total rail count is the rails per section multiplied by the straight-run section count.
total rails = straight-run sections × rails per section
What the rail result is for
The output is a transparent material-planning quantity for one continuous run. It is not a structural design, a spacing specification for every fence system, or a substitute for product instructions and local requirements.
Check the inputs before using the count
Confirm the fence height and post spacing, then enter gate count and gate width so the calculator can remove openings from the straight run. Review the result with posts, infill, concrete, and fasteners before creating a final materials order.