Understanding your result
The run is divided into equal sections no longer than the maximum spacing. Posts include both ends. Rail pieces are counted per section, while pickets cover the full face of the run with the entered gap.
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.
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
- Measure one straight run without gates or corners.
- Enter the maximum span allowed by your fence design and rails per section.
- Enter actual picket dimensions and review separate gate and corner requirements.
Corners, gates, and shared posts
Calculate straight segments individually, then reconcile shared corner posts so they are counted once. Gates can need separate posts and their own hardware. Simply subtracting gate width from a long fence does not correctly describe all post locations. A closed loop also differs from the open run used here.
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.
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.
What to keep in mind
- Does not size posts, holes, foundations, or structural connections.
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.