How Many Fence Posts, Rails and Pickets Do I Need?
A 150 ft wood privacy fence with posts every 8 ft needs about 20 posts (plus one per gate), 57 rails and 345 pickets. Here's how each number is worked out. The fence calculator does it for any length, style and post size.
Posts
sections = fence length ÷ post spacing, rounded up
posts = sections + 1 + one per gate
150 ÷ 8 = 18.75, so 19 sections and 20 posts. Each gate needs its own post on the far side of the opening, so with one gate you'd buy 21. Add a post for every corner that doesn't fall on a regular post position.
- Spacing: 8 ft is standard for wood fences. Use 6 ft for heavy board-on-board fences, windy sites, or to match 6 ft panels.
- Length: posts should be buried about a third of their height above ground, deeper in frost areas. A 6 ft fence typically uses 8 ft posts set 2–3 ft deep.
- Material: use pressure-treated posts rated for ground contact. Gate posts benefit from 6 × 6 or a steel post.
Rails
Rails are the horizontal 2 × 4s between posts that the pickets attach to. Fences up to about 5 ft usually use 2 rails per section; 6 ft privacy fences use 3. For 19 sections × 3 rails = 57 rails, 8 ft long.
Pickets
pickets = fence length (in) ÷ (picket width + gap)
For a privacy fence with 1 × 6 pickets (5.5 inches actual) and no gap: 1,800 ÷ 5.5 = 328 pickets. Add 5% for culls and splits: about 345. For a classic picket fence with 3.5 inch pickets and 2.5 inch gaps, divide by 6 instead.
Board-on-board fences overlap pickets so there's no see-through gap as the wood shrinks; they use roughly 30–50% more pickets.
Concrete
A 4 × 4 post in a 10 inch wide, 3 ft deep hole takes about 1.4 cubic feet of concrete, a bit under three 80 lb bags. For 21 posts with 10% extra, that's about 54 bags of 80 lb concrete. The concrete calculator's Post holes mode works this out for other sizes.
Many builders put 3–4 inches of gravel in the bottom of each hole for drainage, and crown the concrete at the top so water runs away from the post.
Hardware
- Fasteners: exterior-rated screws or ring-shank nails, two per picket per rail. For 345 pickets on 3 rails, that's about 2,100.
- Rail brackets if you're not toe-nailing rails to posts.
- Gate kit: hinges, latch and a drop rod for double gates.
- Post caps to keep water out of the end grain.
Before you dig
- In the US, call 811 a few days ahead to get buried utility lines marked for free.
- Confirm your property line and check local height, setback and HOA rules.
- Many towns expect the "good side" of the fence to face the neighbor or the street.