Fence Picket Calculator
How many pickets, rails and posts a fence needs — for butted or spaced palings — with the exact gap to make it come out even.
How many palings to buy.
How the fence picket calculator works
Picket count is the fence length divided by the picket width plus its gap. The subtlety is making the last picket land flush: dividing the length by a whole number of pickets and back-solving the gap gives an even run instead of a narrow rip at the end.
Rails run the full length at each row, and posts go in at the chosen spacing plus one to finish.
Formula: pickets = length / (width + gap)
Worked examples
| Inputs | Pickets needed | Note |
|---|---|---|
| 20 m butted paling fence, 90 mm palings | 235 | 234 palings |
| With a 20 mm gap | 192 | about 190 |
| A short run | 51 | 48 pickets |
FAQFrequently asked questions
How many palings for a 20 m fence?
About 223 at 90 mm butted, or 190 with a 20 mm gap — plus a waste allowance.
How do I avoid a narrow last picket?
Divide the run by a whole number of pickets and adjust the gap slightly. This calculator gives that exact gap.
What post spacing should I use?
2.4 m is standard for timber fences. Closer for exposed sites or heavy panels.
How many rails?
Two for fences up to about 1.2 m, three above that. Solid paling fences at 1.8 m almost always use three.
Should I leave a gap?
A small gap lets timber expand and lets wind through, which reduces the load on the posts. Butted palings will cup and gap themselves anyway as they dry.
Where these figures come from
- The Engineering ToolBox — material densities, coverage and unit data — bulk densities, concrete at 2,400 kg/m³, board and sheet sizes
- Gypsum Association — gypsum board sizes — 4 × 8 and 4 × 12 ft sheets
- ADA Standards for Accessible Design — ramps (§405) — maximum running slope 1:12
- International Code Council — the International Residential Code
Last checked: September 2026. Coverage rates and material sizes are typical manufacturer figures — check the product you buy.