How many fence posts and pickets do I need?
Posts = total length ÷ post spacing, rounded up, plus one. A 100 ft fence at 8 ft spacing is 12.5, rounds to 13 sections, so 14 posts. Every gate adds one more post.
Pickets = total length in inches ÷ (picket width + gap). For a privacy fence with no gaps using 5.5 in boards, a 100 ft run is 1,200 ÷ 5.5 = 219 pickets.
Rails = sections × rails per section. A 6 ft fence uses three rails, so 13 sections needs 39 rails — usually bought as 8 ft stock matching the post spacing.
Concrete: a 10 in diameter hole 30 in deep takes about 1.2 cubic feet after subtracting the post, which is roughly 3 bags of 60 lb mix per post.
How the calculation works
Post length is fence height plus hole depth. A 6 ft fence with a 30 in hole needs 8.5 ft posts, so you buy 10 ft stock and trim, or 8 ft stock and reduce the hole depth.
Hole depth should be one-third of the total post length and must reach below the local frost line. In northern climates that can mean 42–48 in regardless of fence height — check your county requirement, because frost heave will lift a shallow post out of the ground over a few winters.
Concrete volume assumes a 10 in diameter hole, which suits a 4×4 post. The rule is a hole about three times the post width. Bigger posts and taller fences need wider holes and proportionally more concrete.
The picket count assumes a straight run. Corners, step-downs on slopes and terminating against a house all add cuts, so order about 5% extra.
Typical fence material cost, mid-2026
| Material | Unit | Typical range |
|---|---|---|
| PT 4×4 post, 8 ft | each | $12.00 – $25.00 |
| Cedar 4×4 post, 8 ft | each | $25.00 – $50.00 |
| PT 1×6 picket, 6 ft | each | $2.00 – $5.00 |
| Cedar 1×6 picket, 6 ft | each | $4.00 – $9.00 |
| PT 2×4 rail, 8 ft | each | $6.00 – $12.00 |
| Fast-setting concrete | per 50–60 lb bag | $5.00 – $8.00 |
| Gate hardware kit | per gate | $25.00 – $90.00 |
| Installed privacy fenceLabour included | per linear ft | $25.00 – $60.00 |
What goes wrong on this job
- Set corner and gate posts first, string a line between them, then set the intermediate posts to the string. Setting posts one at a time down the run accumulates error and produces a visibly wavy fence.
- Check the property line before you dig, not after. A fence a foot over the line is a legal problem that ends with you removing it, and a survey costs far less than that.
- Call 811 before digging. It is free, legally required in most of the US, and hitting a gas line with a post-hole digger is exactly as bad as it sounds.
- Gate posts should be one size up — 6×6 rather than 4×4 — and set deeper. A gate hangs its full weight off one post and swings it thousands of times a year, which is why sagging gates are the most common fence failure.
- On a slope, decide between stepping and racking before ordering. Stepped fences need longer posts at the low end; racked fences need pickets cut to varying lengths. Both change the material list.
Frequently asked questions
How far apart should fence posts be?
Eight feet is standard for most residential fence. Drop to 6 ft for 8 ft privacy fence, in high-wind areas, or where the ground is soft.
How deep should fence posts be?
One-third of the total post length, and always below the frost line. A 6 ft fence typically needs 24–30 in in mild climates and 42–48 in where the ground freezes deeply.
How many bags of concrete per fence post?
Two to three 60 lb bags for a 4×4 post in a 10 in hole at 30 in deep. A 6×6 gate post in a 12 in hole needs four to five.
How many pickets do I need for 100 feet of fence?
About 219 using 5.5 in boards butted with no gap, or 145 with a 2 in gap. Add 5% for cuts at corners and terminations.