How fence math works
Posts are fence length ÷ spacing, plus one: a 100-foot run at 8-foot spacing needs 13 posts, not 12, because the run starts and ends with a post. Pickets are total fence inches ÷ (picket width + gap). Rails are fence length × rails per section, in feet of rail board.
Spacing and depth guide
- Post spacing: 8 feet is standard for wood; 6 feet for heavier or taller fences.
- Post depth: one-third of the post in the ground is the rule of thumb, with at least 2 feet for a 6-foot fence.
- Gates: use larger posts and gate hardware rated for the gate's weight — a sagging gate is almost always an undersized post.
Frequently asked questions
How many pickets for 100 feet of 6-inch privacy fence?
100 feet is 1,200 inches ÷ 6 inches = 200 pickets, before the 10% spare allowance — so buy about 220.
Do I need concrete for every post?
For a fence that has to stay straight, yes — one bag per post is a safe planning figure, more in sandy or wet soil.