Fence Calculator

Posts = run length ÷ spacing, rounded up, plus one to close the run — a 100 ft fence (30 m) at 8 ft spacing (2.4 m) needs 14 posts. A wood fence runs 6–8 ft (1.8–2.4 m) between posts; panel fences set the spacing for you (the panel width), and wire or rail fences run 6–8 ft, closer in wind-exposed spots.

Divide the run length by one picket’s width plus the gap, then add waste. Solid privacy fences have no gap: a 100 ft (30 m) run in 5½ in (140 mm) pickets set tight needs about 218 pickets, so order around 240 with 10% waste. For a spaced picket fence, add the gap between boards — the calculator handles both and shows the pickets per section.

Two rails (horizontal stringers) for a fence up to about 4 ft, three for a 6 ft privacy fence, one near the top, one near the bottom and one in the middle to stop the pickets bowing. Each rail spans one bay between posts, so total rails = bays × rails per section — the calculator counts them and their total length for you.

A third of the post height, with 24 in (600 mm) a common minimum — a 6 ft fence (1.8 m) wants posts of 8 ft (2.4 m) set 24 in (600 mm) deep. Go deeper in soft ground and for gates, whose posts carry swinging loads and deserve the biggest holes and the most concrete of the run.

A 10 in (250 mm) diameter hole 24 in (600 mm) deep 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; the calculator does it and totals the bags. Slope the top of each collar away from the post so water sheds.

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.

Set the two end (and any corner) posts first, string a line between them at the top and bottom, and space the intermediate posts to the line. Check each post plumb in two directions while the concrete is wet — it is a two-minute fix then and a crowbar job next week.