Fence sections, posts, rails, and pickets
Each run is divided into equal sections no longer than the entered maximum spacing. Separate runs include their own ends; connected mode shares corner posts along one open path. Rails are counted per section and base pickets per run.
After choosing a post-hole design, use the Concrete Calculator for a separate estimate of the concrete volume.
The formula
Pickets are calculated from (run inches + gap) divided by (picket width + gap), rounded upward. That assumes the picket face continues across posts. The extra picket percentage is applied after the base picket count and rounded to a complete piece. For multiple runs, section and base-picket counts are rounded separately per run. Apply the extra picket percentage once to the summed base count. Separate runs need sum(sections) + number of runs posts; a connected open path needs sum(sections) + 1. Material cost uses posts, rail pieces and allowance-adjusted pickets.
Worked example
A 48 ft run with an 8 ft maximum span has six sections, seven posts, and eighteen rails at three per section. With 5.5 inch pickets and 0.5 inch gaps, the base count is 97; a 10% allowance gives 107 pickets.
How to use this calculator
- Choose a measurement system and one run or several editable run rows. Exclude gate openings.
- For several runs, select separate runs or one connected open path with shared corners.
- Set maximum post spacing, rails per section, picket width, gap and spare picket allowance. Enter component prices under Advanced options.
Corners, gates, and shared posts
List each straight run separately. Connected mode shares one corner post between successive runs on one open path; independent mode counts each run’s two ends. Exclude gate openings and estimate gate framing and hardware separately. A closed loop or branched layout needs a project-specific post count.
Coverage and rail lengths
The picket count assumes a continuous single-sided face, including coverage across posts. Inset panels, alternating boards, and shadowbox designs use different geometry. Rail count is the number of pieces needed, not the number of longer stock lengths to purchase. Confirm actual clear spans, joint details, and available lengths before ordering.
Pricing the counted lumber
Advanced options accept prices per post, rail piece and picket. The subtotal uses the whole post and rail counts and the pickets including allowance. It excludes labor, hardware, concrete, gates and delivery.
Assumptions & limitations
What this calculation assumes
- One straight run has two end posts and no gate.
- Pickets cover the full run; post widths are not subtracted.
- Connected mode is one open path; adjacent runs share exactly one corner post. Separate runs have independent ends.
What to keep in mind
- Does not size posts, holes, foundations, or structural connections.
- Closed loops, branches, gate framing, shared gate posts, hardware and post-width deductions are not modeled.
Common questions
Why is there one more post than sections?
An open chain of sections needs a post at every division plus one at each outside end.
Are fasteners and concrete included?
No. Those depend on the chosen fence system, post-hole design, and manufacturer instructions; count them separately.
Sources & further reading
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