A fence is a handful of counts off two measurements — the run length and the post spacing. That gives you the posts and the concrete; a wood/picket fence adds the rails and the pickets (boards) on top. Here is the whole material list, and how each part is worked out.
Wood or panel?
A wood/picket fence is built up on site — posts, horizontal rails, and vertical pickets nailed to the rails — so you count all three. A panel fence drops pre-made panels between the posts, so you only count posts, panels and concrete. The method for posts and concrete is the same either way; the pickets and rails are the extra a wood fence needs.
How many posts
Posts = run length ÷ spacing, rounded up, plus one to close the run. A 100 ft fence (30 m) at 8 ft (2.4 m) spacing needs 14 posts. Wood fences run 6–8 ft (1.8–2.4 m) between posts; panel fences set the spacing for you (the panel width), closer in wind-exposed spots.
How many rails
Rails are the horizontal stringers the pickets nail to. Use two for a fence up to about 4 ft, three for a 6 ft privacy fence — top, bottom and middle, to stop the pickets bowing. Each rail spans one bay between posts, so total rails = bays × rails per section. A 100 ft fence (13 bays) with 3 rails needs 39 rails, each one bay long.
How many pickets (boards)
Divide the run length by one picket’s width plus the gap, then add waste. A solid privacy fence has no gap: a 100 ft (30 m) run in 5½ in (140 mm) pickets set tight needs about 218 pickets — order around 240 with 10% waste. For a spaced picket fence, add the gap between boards.
| Board | Face width |
|---|---|
| Nominal 1×4 | ~3½ in (89 mm) |
| Nominal 1×6 | ~5½ in (140 mm) |
| Dog-ear / picket | varies — measure it |
Fence Calculator
Enter the run length for posts, rails, pickets and the concrete bags — wood/picket or panel fence.
How deep, and the concrete per post
Set posts a third of their height deep, with 24 in (600 mm) a common minimum — a 6 ft fence wants 8 ft posts set 24 in deep. A 10 in (250 mm) hole at that depth holds about 1 ft³ (0.03 m³) around the post — roughly two 80 lb (40 kg) premix bags. Multiply by the post count for the order, and slope each collar away from the post so water sheds instead of pooling against the timber.
Concrete or rammed earth?
Concrete for gates, corners and anything structural or in soft ground; well-rammed earth or gravel works for intermediate posts in firm ground and drains better around timber. Treated timber posts last longer with gravel at the base of the hole either way — standing water is what rots them.
Keeping the run straight
Set the two end (and any corner) posts first, string a line between them at top and bottom, and space the intermediate posts to the line. Check each post plumb in two directions while the concrete is still wet — it is a two-minute fix then and a crowbar job next week. Gates and corners carry the real loads, so give them deeper holes and more concrete than the run.