Enter your total fence length, post spacing, rails per section, and style, and get the
number of posts, rails, pickets, and bags of concrete it takes. The numbers use the
standard residential fence-building rules — posts 6 to 8 feet on center, two or
three rails per section, 5½-inch pickets — for a straight run, so you can
add posts for your corners and gates.
Read this first
These are estimates for a single straight fence run, based on standard spacing and picket
rules — not a substitute for your own measurements or a fence plan. The post count is
for a straight line: add one post for every corner and two for every gate. Buy a
little extra picket and concrete — trimming the last section and the odd bad board
eat into the count. Confirm how deep to set your posts against your local frost line and
building code; that drives how much concrete each hole really takes.
The calculator
Estimate posts, rails, pickets & concrete
Enter your fence length in feet, pick the post spacing and rails per section, choose a style, and tweak the picket width and gap if your boards differ. You'll get the full material count for a straight run.
The full length of one straight run, post to post.
Post spacing
Rails per section
Fence style
5½″ is the standard dog-ear / picket width.
½″ gap for a spaced picket fence; 0 for solid privacy.
Sections (length ÷ spacing)
Line posts (straight run)
Rails
Pickets
Concrete (50 lb bags)
Straight-run estimate. Add one post per corner and
two posts per gate (a hinge post and a latch post), and a bag or two
of concrete for each — corner and gate holes are usually dug deeper.
How it works
How the counts are figured
It all starts with sections — the spans of fence between posts.
The number of sections is ceil(length ÷ spacing): a 100-foot run at
8-foot spacing is ceil(100 / 8) = 13 sections. You round up because a
partial last span still needs its own pair of posts and a full run of rails. The number
of line posts for a straight run is sections + 1 —
one extra post closes the final section.
Rails are sections × rails per section. Each section
spans one rail run between two posts, so 13 sections with 3 rails is 39 rails. Use 2
rails for a fence about 4 feet tall or shorter and 3 for taller fences, so the pickets
don't bow between supports.
Pickets come from coverage. The space one picket covers is
picket width + gap — 5½″ plus a ½″ gap is
6″ for a spaced fence, or 5½″ with no gap for solid privacy. The
count is ceil(length × 12 ÷ coverage), so a 100-foot spaced
fence is ceil(1200 / 6) = 200 pickets, and the same length in solid privacy
is ceil(1200 / 5.5) = 219.
Concrete is about posts × 2 — roughly two
50-lb bags of fast-setting concrete per hole, assuming a hole about one-third the post
height and 8–10″ across. Bigger or deeper holes use more, so treat this as a
floor and round up for tall, windy, corner, and gate posts.
Post spacing and what it costs you
Two common spacings, and what each does to a 100-foot run. Closer posts make a stiffer
fence but mean more posts, more holes, and more concrete. These figures use the same
formulas as the calculator above.
Spacingon center
Sections100 ft run
Line postsstraight run
Best for
8 ft
13
14
Standard wood fences; matches 8-ft rail stock with no cutting.
Sections are ceil(100 ÷ spacing); line posts are sections + 1 for a straight run.
Going from 8-ft to 6-ft spacing on a 100-foot fence adds 4 posts — and 4 more holes
to dig and set. Spacing wider than 8 ft is not recommended for wood, because the rails
start to sag.
Picket coverage and rails by fence height
How much fence one picket covers depends on its width plus the gap, and how many rails you
need depends on the fence height. Picket counts below are for a 100-foot run, rounded up
to whole pickets — matching the calculator.
Style / picket
Coveragewidth + gap
Pickets100 ft run
Railsby height
Spaced 5½″ + ½″ gap
6.0 in
200
3 rails if over 4 ft
Solid privacy 5½″ + 0 gap
5.5 in
219
3 rails (usually 6 ft)
Spaced 3½″ + 2½″ gap
6.0 in
200
2 rails if 4 ft or under
Pickets are ceil(100 × 12 ÷ coverage). Coverage is picket width plus gap, so a
narrower picket with a bigger gap can land on the same coverage as a wide one with a small
gap. Rails: 2 for a fence about 4 ft or shorter, 3 for taller so the pickets stay flat.
Reading the result well
A material count is only useful if you act on it sensibly. Four things worth knowing
before you buy.
This is a straight-run count — add for corners and gates
The post figure assumes one unbroken line. Real fences turn corners and have gates, and each needs its own post. Add one post for every corner, and two for every gate opening — a hinge post and a latch post, both usually set deeper and in more concrete because a swinging gate puts heavy leverage on them. Count corners and gates off your plan and add them on top.
Closer spacing buys stiffness, not just more posts
Eight-foot spacing is standard because rails and lumber come in 8-foot lengths, so a section spans one rail with no cutting. Drop to 6-foot spacing for tall privacy fences, windy exposure, or ground that isn't flat — the fence resists racking and sag much better. The trade is real: 6-foot spacing adds roughly a quarter more posts, holes, and concrete over the same run.
Match rails to the fence height
Two rails — one high, one low — are enough for a fence about 4 feet or shorter. Go to three rails for anything taller, including most 6-foot privacy fences, so the pickets don't bow or warp between supports over time. The rail count multiplies across every section, so this choice moves your lumber order more than the post count does.
Buy whole pickets and extra concrete — don't under-buy
The calculator rounds pickets and bags up, because you can't buy a fraction. Buy a few extra pickets on top: the last section gets trimmed, and lumber yards always slip in a warped or cracked board or two. Concrete is two bags per hole as a floor — deep corner and gate holes can take three or four. Running short mid-project means a second trip and posts that set on different days.
Where to buy
Got your numbers? Here's where to pick up what you need:
The terms behind the calculator, in plain English. These are background definitions, not
a building specification — follow your local building code and any HOA or property-
line rules for the real thing.
Section (bay)
One span of fence between two adjacent posts. The number of sections is the total length divided by the post spacing, rounded up — the partial last span still counts as a full section for the post and rail math.
Line post
A standard post along a straight run. For a straight line the count is sections + 1, since one extra post closes the final section. Corner posts and gate posts are separate and added on top.
Post spacing (on center)
The distance from the center of one post to the center of the next. 8 feet is standard for wood fences because it matches 8-foot rail stock; 6 feet makes a stiffer fence for tall, windy, or uneven sites.
Rail (stringer)
A horizontal member running between posts that the pickets attach to. Fences use 2 rails up to about 4 feet tall and 3 rails when taller. The total is sections × rails per section.
Picket (board)
A vertical board fastened to the rails. The standard width is 5½ inches (a nominal 1×6). How many you need depends on the coverage, not just the length.
Picket coverage
How much fence one picket covers: picket width + gap. A 5½″ picket with a ½″ gap covers 6″; the same picket with no gap (solid privacy) covers 5½″. Coverage is what the picket count divides by.
Solid privacy vs. spaced picket
A solid privacy fence butts pickets together with no gap for a full screen; a spaced picket fence leaves a small gap between boards for an open, traditional look. Same posts and rails — the gap just changes how many pickets you buy.
Frost line / post depth
The depth to which the ground freezes locally. Posts are typically set below it — often a third of the post height — so frost heave can't push them up. Depth drives how much concrete each hole takes, so confirm it against your local building code.
Frequently asked
For a straight run, the number of line posts is the number of sections plus one. Divide the total length by the spacing and round up to get the sections, then add one for the post that closes the last section. A 100-foot fence at 8-foot spacing is ceil(100 / 8) = 13 sections, so 14 posts. That's a straight line only — every corner needs its own post, and every gate needs two. Try it in the calculator.
Eight feet on center is standard for most wood fences, because pre-cut rails and lumber come in 8-foot lengths, so a section spans one rail with no cutting. Six-foot spacing makes a stiffer, stronger fence — a good choice for tall privacy fences, windy sites, or uneven ground — at the cost of more posts and more digging. Spacing wider than 8 feet isn't recommended for wood fences, because the rails start to sag.
It depends on the picket width and the gap. The space one picket covers is the picket width plus the gap. With a standard 5½″ picket and a ½″ gap, each covers 6″, so you need two pickets per foot. For a solid privacy fence the pickets butt together with no gap, so a 5½″ picket covers 5½″ and you need about 2.18 per foot. The calculator multiplies the length by 12, divides by the coverage in inches, and rounds up.
A common rule of thumb is about two 50-lb bags of fast-setting concrete per post hole. That assumes a hole dug to roughly one-third of the post height and 8 to 10 inches in diameter, typical for a residential wood fence. Bigger posts, deeper holes for tall or windy fences, and wider diameters all use more — a deep corner or gate post can take three or four bags. This calculator uses two bags per post, so scale it up if your holes are larger. See post depth.
Yes. This calculator estimates a single straight run, where posts equal sections plus one. Real fences turn corners and have gates, and each needs its own post. Add one post for every corner where the fence changes direction. Add two posts for every gate — a hinge post on one side and a latch post on the other — and these are often set deeper and in more concrete, because a swinging gate puts heavy leverage on them. Count your corners and gates off your plan and add those posts on top of the calculator's figure.
Two rails are enough for a fence about 4 feet tall or shorter — one near the top and one near the bottom. Fences taller than about 4 feet, including most 6-foot privacy fences, use three rails so the pickets don't bow or warp between supports. The total rail count is the number of sections times the rails per section, because each section spans one rail run between two posts. A 100-foot fence at 8-foot spacing with 3 rails is 13 × 3 = 39 rails.
Divide the total length by the spacing and round up. A section is the span between two adjacent posts, so a 100-foot run at 8-foot spacing is 100 ÷ 8 = 12.5, rounded up to 13 sections. Rounding up matters because a partial section still needs a full pair of posts and a full run of rails. The last, shorter section just gets trimmed rails and fewer pickets, but it still counts as a section for the post and rail math.