How to estimate fence materials
- Measure the fence line in feet. For fences with several runs, add the lengths together (corners are counted automatically as posts along the line).
- Choose post spacing. 8 ft is standard for wood privacy fences; 6 ft gives a stiffer fence in windy areas. Vinyl and pre-built panels set their own spacing — enter the panel width.
- Set rails and pickets. Two rails suit fences up to about 5 ft; 6 ft privacy fences usually use three.
- Enter the hole size to get concrete for setting the posts.
Fence formulas
Posts = Sections + 1 (+ 1 per gate)
Rails = Sections × Rails per section
Pickets = Fence length (in) ÷ (Picket width + Gap)
Worked example: 100 ft privacy fence
100 ft at 8 ft spacing is 13 sections, so you need 14 posts (plus one per gate) and 39 rails with three per section. Side-by-side pickets 5½ in wide need 219 pickets. Setting each post in a 10 in hole 2 ft deep takes about 0.92 cu ft of concrete — roughly 2 bags of 80 lb mix per post.
Fence material chart
8 ft spacing, 3 rails, 5½ in pickets with no gap, no gates:
| Fence length | Posts | Sections | Rails | Pickets |
|---|---|---|---|---|
| 50 ft | 8 | 7 | 21 | 110 |
| 100 ft | 14 | 13 | 39 | 219 |
| 150 ft | 20 | 19 | 57 | 328 |
| 200 ft | 26 | 25 | 75 | 437 |
| 300 ft | 39 | 38 | 114 | 655 |
How deep should fence posts be?
A common rule is to bury one third of the post's above-ground height — about 2 ft for a 6 ft fence, using 8 ft posts — and at least below the frost line where the ground freezes. Make the hole about three times the post's width (10–12 in for a 4×4). Check your local code and call 811 before digging to locate buried utility lines.
Tips
- Use ground-contact rated pressure-treated posts for wood fences.
- Gate posts carry more load: consider 6×6 posts and deeper holes.
- For shadowbox or board-on-board fences the pickets overlap, so you need roughly twice the side-by-side count.
- Check property lines, HOA rules and height limits before building.
Frequently asked questions
How many fence posts do I need for 100 feet?
At 8 ft spacing, a straight 100 ft fence needs 14 posts — one more than the 13 sections — plus an extra post for each gate.
How many pickets do I need for a fence?
Convert the fence length to inches and divide by the picket width plus any gap. A 100 ft fence with 5½ in pickets and no gap needs 219 pickets; add about 5% extra for bad boards.
How far apart should fence posts be?
6–8 ft for wood fences, with 8 ft the most common. Vinyl and metal panels dictate their own spacing, typically 6 or 8 ft.
How much concrete per fence post?
A 10 in hole 2 ft deep with a 4×4 post takes about 0.92 cu ft — around 2 bags of 80 lb concrete or 3 bags of 60 lb.
How many rails does a 6 ft fence need?
Three rails per section — top, middle and bottom — for a 6 ft wood privacy fence. Fences up to about 5 ft typically use two.