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Board-on-Board Fence Calculator

Boards on both faces, each lapping the two behind it — how many, and what holds them up.

An estimate of material — the overlap is yours to set under Assumptions.

100' · 1200 in · 100 ft · 30.48 m

100 ft

5% covers pickets split by a screw or culled for warp and knots. It is added once, to the pickets — the posts, rails and concrete are counted from the fence itself.

This page recalculates as you type. There is no Calculate button.

Answer

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Pickets, with waste

281 pickets

100 ft of fence · 13 bays · 14 posts in holes 42" deep

Posts 14 posts
Rails 39 2×4s · 3 a bay
Fence, gates left out 100 ft
Concrete 47 × 50 lb fast-setting
Gravel under the posts 8 × 50 lb bags (0.5 ft³)
Ticked items cost $1,652.20
More numbers
Post holes 42" deep, 10" across
Widest post spacing 7' 8 5/16" on center
DrawingThe project drawn to scale. Run 1: 100' × 6'.100'6'Run 1

Buying noteCall 811 a few business days before you dig. It is the free national before-you-dig service: the utilities mark their lines, and every post hole needs it.
Buying noteYour frost depth is not set. Where the ground freezes, a post set above the frost line heaves: ask your building department for the depth (IRC Table R301.2(1)) and type it under Assumptions — every hole follows it.

Breakdown

Run or gate Measurements Qty Length Share
Run 1 100' Add ×1 100 ft

What to buy

Buying noteCall 811 a few business days before you dig. It is the free national before-you-dig service: the utilities mark their lines, and every post hole needs it.
Buying noteYour frost depth is not set. Where the ground freezes, a post set above the frost line heaves: ask your building department for the depth (IRC Table R301.2(1)) and type it under Assumptions — every hole follows it.

Ways to buy the concrete

The bags for every post hole together, by the shape of the holes. Every way is worked out; pick the one you will buy.

47 × 50 lb fast-setting Bags 47 Left over 0.17 ft³ Weight 2,350 lb Cost $375.06 Reference price $7.98. Type your store's.

Shopping list

14 14 × 10 ft $236.60 Reference price $1.69. Type your store's.
281 281 × 6 ft $640.68 Reference price $0.38. Type your store's.
39 39 × 8 ft $187.20 Reference price $0.60. Type your store's.
5 3 × 5 lb box (453) + 2 × 1 lb box (126) $135.85 Reference price $10.97. Type your store's. Reference price $37.97. Type your store's.
1 1 × 5 lb box (309) $32.97 Reference price $32.97. Type your store's.
14 14 × 4×4 caps $111.72 Reference price $7.98. Type your store's. Reference price $12.98. Type your store's.
47 47 × 50 lb fast-setting $375.06
8 8 × 50 lb bags (0.5 ft³) $43.84 Reference price $5.48. Type your store's.
Ticked items $1,652.20

Untick what you already have. Lumber is priced by the foot, beside its row; the concrete's bags are priced in the table above.

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How this was worked out

Every number below is yours. Each constant links to the row where you can change it.

Run 1 100' 100 ft
Posts 13 bays in 1 runs: 12 line + 2 end + 0 corner + 0 gate 14 posts

Change:Widest post spacing, wood

How deep a post goes 0.5 × 72" out of the ground, or the frost depth 0" where deeper 36" + 6" = 42"

Change:Post in the ground, share of its height aboveYour frost depthGravel in the bottom of a hole

Posts, length 72" + 36" = 108" 14 × 10 ft
Concrete, each post (π ÷ 4 × 10" × 10" − 3 1/2" × 3 1/2") × 32 1/2" 1.247 ft³ × 14 = 17.455 ft³

Change:Hole across, 4×4 postConcrete stops under the ground

Bags of concrete 17.455 ft³ ÷ 0.375 ft³ 46.55 → 47 × 50 lb fast-setting

Change:Yield, 50 lb fast-setting bag

Gravel under the posts π ÷ 4 × 10" × 10" × 6" × 14 3.818 ft³ → 8 × 50 lb bags (0.5 ft³)

Change:Gravel in the bottom of a hole

Rails 13 × 3 = 39 39 × 8 ft

Change:A rail every

Pickets, edge to edge (1200" − 1") ÷ (5 1/2" − 1") 267 × 6 ft

Change:Board-on-board overlapGap under the pickets

With the waste for culls 267 × (1 + 5%) 280.35 → 281
Screws 267 pickets × 3 rails × 2 + 39 boards × 2 ends × 2 1,602 + 156

Change:Screws where a picket crosses a railScrews at each end of a rail

What it comes to 14 × 10 ft × $1.69/ft + 281 × 6 ft × $0.38/ft + 39 × 8 ft × $0.60/ft + 3 × $37.97 + 2 × $10.97 + 1 × $32.97 + 47 × $7.98 + 8 × $5.48 $1,652.20

Assumptions

Every one of these is editable. Change one and the answer changes with it.

Assumption Value Confidence
Widest post spacing, woodPosts of a wood fence no more than 8 ft apart, center to center: the spacing Inch Calculator and Omni both work at, and the length of the 2×4 rail that spans a bay. ≈ in Trade convention
A rail everyOne rail for every 24 in of fence height, never fewer than a top and a bottom one: Inch Calculator's rule - three rails on a 6 ft fence, two up to 4 ft. ~ in Derived or single-supplier
Board-on-board overlapHow far each board of a board-on-board fence laps the two behind it. Omni's board-on-board calculator laps about a quarter of the board's width. ~ in Derived or single-supplier
Gap under the picketsPickets stop about 2 in above the ground so they do not wick water; Freedom's vinyl kit sets its panels about 2 in up, and 2 in is the most ISPSC 305.2.1 allows over grass or gravel. ≈ in Trade convention
Screws where a picket crosses a railTwo screws where each picket crosses a rail, the usual nailing of a privacy fence. ~ screws Derived or single-supplier
Screws at each end of a railTwo screws at each end of a rail or a gate board, into the post or the frame. ~ screws Derived or single-supplier
Post in the ground, share of its height aboveQuikrete Fast-Setting Concrete Mix spec sheet, section 5: a post hole one half as deep as the post stands above ground. Quikrete's Setting Posts sheet says the same as one third of the post's length, and so does Home Depot's chain link guide for its posts. ratio From a data sheet or an agency document
Your frost depthYour frost depth, from your building department (IRC Table R301.2(1) is filled in locally). 0 means not given: every hole is then as deep as the post's own rule. Typed in, no hole stops above it. ≈ in Trade convention
Gravel in the bottom of a holeQuikrete Setting Posts, step 2: 6 in of gravel or crushed stone in the bottom of the hole, for drainage. in From a data sheet or an agency document
Concrete stops under the groundQuikrete Setting Posts, steps 4 and 6: fill the hole to 3-4 in below the top, then finish with soil. The middle of the range. in From a data sheet or an agency document
Hole across, 4×4 postQuikrete Fast-Setting spec sheet, section 3: a 4 in post set in a 10 in hole. Its rule of three times the post would make 10½ in for a 4×4. in From a data sheet or an agency document
Hole across, 6×6 postA 6×6 gate post. Quikrete's three times the post would be 16½ in, a hole few dig for a fence; 12 in is an auger's size. ~ in Derived or single-supplier
Yield, 50 lb fast-setting bagQuikrete Fast-Setting Concrete Mix spec sheet. ft³/bag From a data sheet or an agency document

How many boards a board-on-board fence takes

A board-on-board fence hangs its pickets on both faces of the rails, each board lapping the two behind it, so it is the privacy fence's count with the gap taken away. With 5½ inch boards lapped 1 inch, each one adds 4½ inches of fence past the one before: 100 feet is (1,200 − 1) ÷ (5.5 − 1) = 266.4, so 267 boards for both faces together — 281 with 5% for culls. The same fence built tight on one face takes 219, so the second face costs about a fifth more lumber.

Everything behind the boards is the privacy fence's: 14 posts, 13 bays of 7' 8 5/16", three 2×4 rails a bay for 39 rails, and 47 bags of fast-setting concrete in holes 42 inches deep. The rails carry boards on both sides, so they are worth buying straight and screwing well: two screws where each board crosses a rail is 267 × 3 × 2 = 1,602 screws.

The lap is yours to set

The page laps each board 1 inch. Omni's board-on-board calculator laps about a quarter of the board's width — closer to 1⅓ inches on a 1×6 — and some builders lap 1½. At 1½ inches the same 100 feet takes 300 boards, 315 with the culls. The lap is the Board-on-board overlap under Assumptions; change it and every count follows. Boards shrink as they dry, and a lap is what keeps a gap from opening between them, which is the reason to build this fence at all: it stays private from every angle.

Shadowbox is the same arithmetic

A shadowbox fence alternates boards from one face to the other with a gap on each face narrower than a board. Seen straight on it is closed; seen at an angle it lets air through. Counted, it is the same: boards edge to edge along the line with a lap where they overlap. Type the overlap you mean — a ½ inch lap for a looser shadowbox — and the page counts the boards for both faces. We are not connected with any maker, store or supplier named here.