Reference formulas and worked examples below keep their stated units. Monetary examples use USD; dimensional examples use US customary units unless labeled otherwise. Metric calculator inputs are converted to these reference units before calculation. Choosing another currency does not convert example amounts or exchange money.
How to use this fence picket calculator
The installed count covers the run using full-width pickets and the target gap. The ordering count rounds an optional waste allowance up to whole boards.
How the calculation works
Convert run length to inches. The minimum installed count is rounded up from (run inches + gap) ÷ (picket width + gap).
That count covers installed count × board width + (installed count − 1) × target gap. Any extra coverage becomes a cut at the end.
Apply the waste percentage to installed pickets and round the ordering quantity up to whole boards.
Worked example
A 100 ft run uses 1,200 in. With 5.5 in actual pickets and 0.25 in gaps, 209 pickets cover 1,201.5 in, so the last picket needs about 1.5 in trimmed. At 10% extra, order 230 pickets.
Limits and assumptions
One straight run only. Gates, corner and end posts, rails, fastening, local fence rules, and board-on-board overlap are not included. Calculate each separate run independently.
Frequently asked questions
Should I enter a nominal or actual board width?
Enter the measured visible face width. Nominal lumber names often differ from the actual finished width.
Does this count gate openings?
No. Subtract gate openings from each uninterrupted run before calculating; do not include a gate as a picketed section.
Why is there an end trim?
Whole boards and fixed gaps may cover slightly more than the measured run. The final board can be trimmed to fit.