How many pickets do I need for 100 feet of fence?

219 at 5½ in wide butted tight. A board-on-board layout with a 1 in overlap needs about 267, and shadowbox closer to 320.

How deep should fence posts be?

One third of the above-ground height as a baseline: 2 ft for a 6 ft fence. Where the ground freezes, go below the local frost depth instead, which is often deeper and is what actually stops the fence heaving.

How many bags of concrete per fence post?

For a 10 in hole 2 ft deep with a 4x4 post, about 0.92 cu ft, three 60 lb bags. At a 3 ft frost depth it goes to four.

How far apart should fence posts be?

Eight feet on center is the practical maximum for a 2x4 rail carrying full-height pickets. Beyond that the rails sag, and the panel gets heavy enough to work the posts loose.

Do I subtract the post from the concrete volume?

Yes. A 4x4 fills about 16% of a 10 in hole. Ignoring it over-orders by roughly half a bag per post.

Do I need a permit for a privacy fence?

Often not below 6 or 7 ft, but the threshold is local and so are setback rules, corner-visibility rules and any HOA restriction. Being permit-exempt does not make a fence exempt from property-line disputes, which are far more common than code problems.

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Privacy Fence Calculator

Post embedment: one-third rule · frost depth per local adoption

Count the pickets, rails, posts and bags of concrete for a privacy fence. The number that decides whether the fence is still straight in ten years is none of those: it is how deep the posts go.

Fence material takeoff

Total fence length

Fence height (above grade)

Post spacing (on center)

Picket width (actual, a 1x6 is 5.5)

Gap between pickets (0 for full privacy)

Rails per section

Post hole diameter (3x the post is the rule of thumb)

Post width (actual, a 4x4 is 3.5)

Local frost depth (0 if none)

Concrete bag yield (60 lb is 0.45, 80 lb is 0.60)

cu ft

Post embedment defaults to one third of the above-ground height, a long-standing convention rather than a code table. Where the ground freezes, frost depth governs instead, see below.

Privacy fence elevation

Worked example

100 ft of 6 ft privacy fence, posts at 8 ft on center, 1×6 pickets butted tight, three rails per section, 10 in post holes, 4×4 posts, no frost.

Sections and posts. 100 ÷ 8 = 12.5 → 13 sections, which needs 14 posts. The last section is short; spreading the spacing slightly is tidier than leaving a 4 ft stub.
Pickets. 100 ft is 1,200 in; at 5½ in each with no gap that is 219 pickets.
Rails. 13 sections × 8 ft × 3 rails = 312 linear feet of rail.
Post depth. One third of the 72 in height is 24 in, so posts are 6 ft above grade plus 2 ft buried. Buy 8 ft posts.
Concrete. A 10 in hole 24 in deep is 1,885 in³; the post displaces 294 in³, leaving 0.92 cu ft per post. At 0.45 cu ft per 60 lb bag that is 3 bags per post, or 42 bags.

Now enter a 36 in frost depth, as much of the northern US has. The one-third rule still says 24 in, but frost governs: posts go 36 in down, you need 9 ft stock instead of 8 ft, and the concrete rises to 4 bags per post. That is 14 extra bags and a different lumber order, decided entirely by a number that is not on most fence calculators at all.

The formula

Three separate counts, and one volume that people consistently get wrong by forgetting the post itself displaces concrete:

posts = ⌈R/s⌉ + 1 pickets = ⌈ 12R / (w + g) ⌉ V = (π(d/2)²·h − p²·h) / 1728

R: total fence run, ft
s: post spacing on center, ft
w, g: actual picket width and gap, in
d: post hole diameter, in
h: embedment depth, in
p: actual post width, in (a 4×4 is 3.5)
V: concrete per post, cu ft

Subtracting the post volume matters more than it looks. In a 10 in hole a 4×4 takes up about 16% of the space, which is roughly half a bag per post: seven bags across this fence.

Where post depth actually comes from

The one-third rule is convention, not code. Burying one third of the above-ground height (2 ft for a 6 ft fence)is long-standing practice, and it is about resisting the overturning moment from wind on a solid panel. A privacy fence is a sail, and that is precisely why it leans when a picket fence beside it does not.

Frost depth usually governs, and it is local. Where soil freezes, water in it expands and lifts anything anchored above the frost line. The IRC requires footings for buildings to bear below the local frost line (R403.1.4), and while a fence under 7 ft is exempt from permit in many jurisdictions and so is not covered by that section at all, the physics does not care about the exemption. Frost depth runs from zero in the Gulf states to 4 ft or more in northern Minnesota and Maine. Your building department publishes the number for your area; it is worth the phone call before you dig.

Why this page will not print a frost depth table. Frost depth is set by local adoption and local climate data, it varies within a single state, and a table of approximate figures is exactly the kind of thing that gets copied around the web until nobody knows the source. Enter the figure your jurisdiction publishes and the calculator will use it.

Hole diameter of roughly three times the post is the matching convention: a 10 in hole for a 4×4. Wider gives more bearing against overturning; deeper does more than wider, which is why the depth number is the one to get right.

Board-on-board and shadowbox layouts

Butted pickets are the cheapest full-privacy layout and the one this calculator counts by default. Two common alternatives cost more material: board-on-board overlaps each picket over its neighbour by ½ to 1 in, which absorbs shrinkage and needs roughly 15–20% more pickets; shadowbox alternates pickets on either side of the rails, looks the same from both sides, lets air through (a real advantage on an exposed run)and needs close to 50% more.

To count either, work out the effective coverage per picket and enter that as the picket width. A 5½ in board lapped 1 in covers 4½ in, so entering 4.5 gives the right count.

Gates come out separately

No gate is included above. A gate opening needs its own pair of posts, and they should be heavier than the line posts: a 6×6 rather than a 4×4 on the hinge side is normal, because a full-height gate hangs its whole weight off one post and works it every time it swings. Subtract the gate width from the run before counting pickets, and set those two posts deeper than the rest.

Frequently asked questions

How many pickets do I need for 100 feet of fence?: 219 at 5½ in wide butted tight. A board-on-board layout with a 1 in overlap needs about 267, and shadowbox closer to 320.
How deep should fence posts be?: One third of the above-ground height as a baseline: 2 ft for a 6 ft fence. Where the ground freezes, go below the local frost depth instead, which is often deeper and is what actually stops the fence heaving.
How many bags of concrete per fence post?: For a 10 in hole 2 ft deep with a 4×4 post, about 0.92 cu ft, three 60 lb bags. At a 3 ft frost depth it goes to four.
How far apart should fence posts be?: Eight feet on center is the practical maximum for a 2×4 rail carrying full-height pickets. Beyond that the rails sag, and the panel gets heavy enough to work the posts loose.
Do I subtract the post from the concrete volume?: Yes. A 4×4 fills about 16% of a 10 in hole. Ignoring it over-orders by roughly half a bag per post.
Do I need a permit for a privacy fence?: Often not below 6 or 7 ft, but the threshold is local and so are setback rules, corner-visibility rules and any HOA restriction. Being permit-exempt does not make a fence exempt from property-line disputes, which are far more common than code problems.

Check these numbers yourself

AWC DCA 6: Prescriptive Residential Wood Deck Construction GuideAmerican Wood Council, free PDF. The prescriptive deck guide the IRC deck provisions track.
Voluntary Product Standard PS 20: American Softwood Lumber StandardALSC / US Dept of Commerce. The standard that makes a nominal 2x6 measure 1.5 x 5.5 in.

Figures on this page last checked against the source documents on 2026-09-05. Codes are amended locally; confirm against the edition your jurisdiction enforces.

Related calculators

Estimates only. This is a material takeoff for planning and ordering. Post embedment follows the one-third convention and your entered frost depth, neither of which is a substitute for local requirements. Confirm frost depth, height limits, setbacks and permit thresholds with your building department, and check any HOA or property-line restrictions before building.