How many pickets do I need?
Take the fence length in inches and divide it by the width of one picket plus the gap. A 100-foot fence is 1,200 inches. With 5½-inch pickets set edge to edge, that's 1,200 divided by 5.5, which rounds up to 219 pickets. Leave a 2½-inch gap and it's 1,200 divided by 8, so 150.
| Per 100 ft of fence | No gap | 1 in gap | 2 in gap | 3 in gap |
|---|---|---|---|---|
| 3½ in picket | 343 | 267 | 219 | 185 |
| 5½ in picket | 219 | 185 | 160 | 142 |
Those are bare counts. Tick the 10% box above and the calculator adds spares.
A 1×6 is not 6 inches wide
Lumber is sold by its nominal size, and the real board is smaller. A picket labeled 1×6 measures 5½ inches across. A 1×4 measures 3½. Do the math with 6 and you'll come up about one picket short in every twelve.
Rails and posts
Posts go at each end of every section, so a fence always has one more post than sections. With posts 8 feet apart, a 100-foot fence has 13 sections and 14 posts.
Rails are the horizontal 2×4s the pickets fasten to. Two per section is fine for a low fence. A 6-foot fence wants three, or the pickets will warp and bow between them.
Buy posts 2 feet longer than the fence is tall. The extra goes in the ground. The post hole concrete calculator works out the concrete for holes of any size.
Wet boards shrink
Pressure-treated pickets usually come off the stack damp, and they shrink as they dry. Butt them tight today and there will be a small gap between every board in a few months. That's normal.
If you need a fence with no gaps at all, build it board-on-board, with a second layer of pickets covering the joints in the first. It takes roughly half as many pickets again.
Order a few extra
Some boards in every bundle are split, twisted or have a knot right where you need to cut. Ten percent extra is the usual allowance. Most stores take back what you don't use, so being a few over costs you a trip, and being a few short costs you the afternoon.
Fair questions
How many pickets in one 8-foot section?
An 8-foot section is 96 inches. With 5½-inch pickets and no gap that's 18 pickets. With 3½-inch pickets it's 28.
Screws or nails?
Either works. What matters is the coating. Use hot-dipped galvanized or stainless steel fasteners, because the preservative in treated lumber eats through plain steel.
What will the whole fence cost built?
This page prices the materials. For a contractor-built price with labor, use the fence cost calculator.
Sources
- Quikrete, Setting Posts in Concrete: hole width, hole depth and how much concrete a post takes.
- Call 811: the national call-before-you-dig service, for when and how to have buried utilities marked.
