Fence Calculator
This fence calculator counts the posts, rails, and pickets for a wood fence, plus the concrete to set the posts. Enter your total fence length in feet or meters, pick 6- or 8-foot post spacing and two or three rails per section, add your gates, and every line on the materials list updates instantly.
Fence posts needed
21posts
- Rails (2 per section × 19 sections)38 rails
- Pickets (5.5″ wide, 0″ gap)328 pickets
- Concrete — 2 bags per post (rule of thumb)42 × 50 lb bags
Formulas last reviewed on .
How the post, rail and picket counts work
Three short formulas cover the whole materials list:
rails = (posts − 1 − gates) × rails per section
pickets = ceil(length in inches ÷ (picket width + gap))
Dividing length by post spacing gives the number of bays; rounding up handles runs that don’t split evenly, and the +1 is the post that closes the far end — a 150-foot run has 20 posts holding 19 bays before gates. Each gate then adds one more post, because a gate needs two posts of its own and only inherits one from the fence line. Gate openings drop out of the section count, so you’re not buying rails for a bay that’s actually a gate.
Pickets divide the run’s length in inches by one picket’s width plus the gap you leave between them — a true privacy fence butts 5.5-inch pickets tight, so the gap is 0. The concrete line uses the tradesman’s rule of thumb of two 50-pound bags per post; it’s an estimate, not gospel, and deep or wide holes can push it to three.
Worked example: 150 feet of backyard privacy fence
Say you’re enclosing the two open sides of a backyard — 150 feet of 6-foot privacy fence with one walk gate, posts on 8-foot centers, two rails per section, and 5.5-inch pickets butted tight. Those are the defaults loaded above, so you can follow every step in the result box.
- Posts: 150 ÷ 8 = 18.75, rounded up to 19 bays. Add the end post: 20. Add one for the gate: 21 posts.
- Sections: 21 − 1 − 1 gate = 19 fenced sections.
- Rails: 19 × 2 = 38 rails — buy 8-foot 2×4s and they drop in without a cut.
- Pickets: 150 ft = 1,800 inches. 1,800 ÷ 5.5 = 327.3, rounded up to 328 pickets. That count spans the gate bay too, which is fine — you’ll build the gate from the same stock.
- Concrete: 21 posts × 2 bags = 42 fifty-pound bags, by the rule of thumb.
One opinionated tip: buy the posts one size longer than you think you need. A 6-foot fence wants 9-foot posts once a proper third of the height is in the ground — 8-footers leave you an inch short of a solid set.
How much material do I need for a 50 to 300 foot privacy fence?
The chart below assumes the default setup: 8-foot post spacing, two rails per section, 5.5-inch pickets with no gap, one gate, and two 50-pound concrete bags per post. Swap the inputs above for anything different.
| Fence length | Posts | Rails | Pickets | Concrete bags (50 lb) |
|---|---|---|---|---|
| 50 ft | 9 | 14 | 110 | 18 |
| 75 ft | 12 | 20 | 164 | 24 |
| 100 ft | 15 | 26 | 219 | 30 |
| 150 ft | 21 | 38 | 328 | 42 |
| 200 ft | 27 | 50 | 437 | 54 |
| 250 ft | 34 | 64 | 546 | 68 |
| 300 ft | 40 | 76 | 655 | 80 |
Posts don’t scale in a straight line — the end post and gate post are fixed overhead, so short runs carry proportionally more posts per foot. Corners matter too: every direction change ends one straight run and starts another, so price an L-shaped yard as two runs rather than one long one.
Frequently asked questions
How deep should fence posts be set?
Follow the one-third rule: bury a third of the fence’s above-ground height, with 2 feet as the practical minimum. A 6-foot privacy fence wants posts 2 feet down in a hole about 30 inches deep — the extra 6 inches takes a gravel bed for drainage. In cold climates, get below the frost line no matter what the rule says, or frost heave will walk your posts out a little more every winter.
Should fence posts be 6 or 8 feet apart?
Eight feet is standard because rails come in 8-foot lengths and drop between posts without a cut. Choose 6-foot spacing when the fence takes more load: tall solid-privacy panels in windy areas, heavy hardwood pickets, or sloped yards where you rack each section. On the 150-foot example, tightening to 6-foot centers adds 5 posts and 12 rails — the calculator shows the difference instantly.
How many bags of concrete do I need per fence post?
Two 50-pound bags per post is the rule of thumb this calculator uses, and it fits the typical hole: 9 to 10 inches across, about 2 feet deep, around a 4×4. Do the volume math and that hole needs roughly 0.7 to 0.9 cubic feet of mix, and a 50-pound bag yields about 0.375. Gate posts and corner posts take the most strain — give those three bags and a slightly wider hole.
How do I calculate pickets if I want gaps between them?
Add the gap to the picket width before dividing. With 5.5-inch pickets and a half-inch gap, each picket "occupies" 6 inches, so a 150-foot run needs 1,800 ÷ 6 = 300 pickets instead of 328 butted tight. Set the gap in the advanced options and the calculator does exactly this. For shadowbox fences, run the numbers once per side — the two alternating layers each cover the full length.
Do gates change how many posts I need?
Yes — each gate adds one post to the count. A gate hangs between two posts, and only one of them does double duty with the fence line, so the calculator adds one per gate. Build the hinge side stout: a 4-foot gate swinging on a standard line post will sag it out of plumb within a season, so use a 6×6 or steel-reinforced post there and set it in extra concrete.
These results are planning estimates only — verify quantities with your supplier and local building code before you buy or build. See our terms of use.