How this calculator works
Pickets have a fixed face width and a gap between them, so each picket takes its width plus one gap of room along the run. Dividing the run by that pitch and rounding up gives the number of pickets, because the last picket may only partly fit and a spare is cheaper than a second trip. The reverse mode spreads the leftover run evenly: with n pickets at full width, the remaining length is shared between n - 1 gaps. Coverage is the picket width divided by the pitch, so it shows how much of the fence line is actually board.
Formula
Pitch = picket width + gap; pickets = ceil(run / pitch); buy = ceil(pickets x (1 + waste)). Reverse: gap = (run - pickets x width) / (pickets - 1). Coverage = width / pitch.
Worked example
A 30 m run of 140 mm pickets with 20 mm gaps has a 160 mm pitch and needs 188 pickets, which is 87.5% coverage. On a 24 m run with 60 mm gaps, the 200 mm pitch needs 120 pickets and gives 70% coverage.
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Frequently asked questions
Should the first and last pickets sit at the ends of the run?
The forward count assumes a picket starts the run and the last gap may be cut short. The reverse mode spreads the run evenly between the outer picket faces, so both ends line up with a picket.
What gap gives privacy?
None. A privacy fence uses boards edge to edge or overlapping, and shrinkage can still open thin lines. Use the board-on-board or privacy designs when sight lines matter.
Why round the picket count up?
You can only buy whole pickets, and the cut at the end of a run is rarely reusable. The waste allowance then covers damaged or mis-cut pieces.