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.
Metric options use regional material sizes. Check your selected sizes after switching units.
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
Updated .
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 widths are not modeled. The rail count stays based on the full entered run, so treat it as a preliminary allowance and deduct actual gate openings in your layout.
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 — check rail cut lengths against the measured clear span and chosen post connection.
- 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.
Choose post length from the required above-ground height plus embedment and any trimming allowance. Soil, frost depth, wind exposure, and gate loads affect that detail; the post-count estimate does not specify the embedment.
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 6 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.