A fence is a repeating bay — post, rails, pickets — so the whole estimate is counting bays and then counting what fills them. This calculator works out posts, rails, pickets and post-hole concrete for any run of wood fencing, with an allowance to leave a gate opening unpicketted.
The formulas
Posts land at both ends of every section, which is why posts are always sections + 1 on a straight run. When your length doesn't divide evenly by the spacing — it rarely does — the calculator rounds the section count up and reports the true section width, which is what you will actually build; even spacing looks far better than one odd short bay.
Spacing, pickets and rails
8 ft is the standard post spacing for wood fences (6 ft for tall or windy sites); rails are sold to match. Two rails per section suit fences up to about 5 ft; 6 ft privacy fences want three so pickets stay flat. The picket pitch — width plus gap — is the tiler's trick again: a 5.5 in picket with a ½ in gap covers 6 in of fence per picket, which is why pickets per foot is simply 12 ÷ pitch.
Setting the posts
Dig post holes about ⅓ of the post length deep (2 ft for a 6 ft fence) plus 6 in of gravel at the bottom, and budget roughly 1½ × 50 lb bags of concrete per hole at standard 8–10 in auger widths — the figure this calculator uses by default. Posts rot at the ground line, not in the concrete: dome the concrete slightly above grade so water sheds away from the wood.
Worked example
A 100 ft fence at 8 ft spacing: sections = 100 ÷ 8 = 12.5 → 13 sections (7.7 ft each in practice), posts = 14. Two rails per section = 26 rails. Pickets at 5.5 in + ½ in gap = 6 in pitch over 100 ft = 200 pickets. Concrete at 1.5 bags per post = 21 bags.
How to use this tool
- Measure the full run of fence, including where gates will go.
- Choose post spacing — 8 ft standard, 6 ft for tall fences or windy sites.
- Enter picket width and the gap you want between pickets (0 for a board-on-board look is handled by overlapping — see the FAQ).
- Enter any gate width so its pickets are not counted, and the concrete you plan per post.
- Add 5% spare pickets when ordering — a few in every bundle are warped or split.
Before you dig
Call your local utility-locating service (811 in the US) before digging post holes — it is free and legally required in most places. Check your property line and local fence rules (height limits and “finished side out” ordinances are common) before the first post goes in; moving a finished fence costs far more than the posts did.