How to estimate fence materials
A typical wood fence is built in sections. Each section runs between two posts, with horizontal rails fixed between the posts and pickets (also called boards) fastened to the rails. Once you know the total length and how far apart the posts go, everything else follows.
How the calculator works
- Fenced length: it subtracts gate openings from the total length.
- Sections: it divides the fenced length by the post spacing and rounds up.
- Posts: one more post than sections, plus one extra post for each gate, because a gate splits the run in two.
- Rails: sections × rails per section.
- Pickets: fenced length in inches ÷ (picket width + gap), rounded up.
- Concrete: the volume of each hole minus the post, times the number of posts, divided by the bag yield.
The formulas
Typical concrete yields are about 0.60 cubic feet for an 80 lb bag, 0.45 for 60 lb, 0.375 for 50 lb and 0.30 for 40 lb. Check the bag, since mixes vary.
Worked example
You are building 150 ft of 6 ft privacy fence with one 4 ft gate, posts every 8 ft, three rails per section and 5½ inch pickets with no gap.
Fenced length: 150 − 4 = 146 ft. Sections: 146 ÷ 8 = 18.25, rounded up to 19. Posts: 19 + 1 + 1 = 21. Rails: 19 × 3 = 57. Pickets: 146 × 12 ÷ 5.5 = 318.5, rounded up to 319.
A 10 inch hole with 2 ft of concrete around a 4×4 post takes about 0.92 cubic feet, or roughly 1.5 bags of 80 lb mix per post, so about 33 bags for 21 posts.
Tips for a better estimate
- Corners and separate runs. The calculator assumes one continuous line. A corner post is shared by both sides, so corners in a continuous run do not add posts, but if you have separate, unconnected runs, add one extra post for each additional run.
- Hole depth. A common guide is to bury about one-third of the post's total length, and below your local frost line where it applies. Many 6 ft fences use 8 ft posts set 2 to 3 ft deep.
- Shadowbox and board-on-board fences overlap pickets on both sides of the rails, so they need roughly twice as many pickets. Increase the estimate accordingly.
- Extra for waste. Order 5–10% extra pickets for split boards and cuts.
- Check the rules first. Many towns and homeowners associations limit fence height and placement, and some require a permit. In the U.S., call 811 before digging to have underground utilities marked.
Frequently asked questions
How many fence posts do I need?
Divide the fence length (minus gates) by your post spacing, round up to get the number of sections, then add one post, plus one more for each gate. A 100 ft fence with 8 ft spacing and no gates needs 14 posts.
How far apart should fence posts be?
Most wood fences use 6 to 8 feet between posts. Wider spacing saves posts but can make rails sag; check your material instructions.
How many bags of concrete per fence post?
For a 10 inch hole with 2 feet of concrete around a 4×4 post, about 1.5 bags of 80 lb concrete. Wider or deeper holes need more.
How many pickets do I need per foot?
With 5½ inch pickets and no gap, about 2.2 pickets per foot of fence. With 3½ inch pickets and a 2½ inch gap, 2 per foot.
Does this include gates?
It removes the gate openings from the picket and rail count and adds the extra posts. The gates themselves, along with hinges and latches, are separate.
Last reviewed November 2026. Spotted an error? Tell us.