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Picket Fence Calculator

A front-yard picket fence and its gate — the pickets, and the even gap to space them at.

An estimate of material — check your town's rules for a fence near the street.

30' · 360 in · 30 ft · 9.144 m

30 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

65 pickets

30 ft of fence · 4 bays · 5 posts in holes 27" deep

Posts 5 posts
Rails 8 2×4s · 2 a bay
Fence, gates left out 30 ft
Concrete 9 × 50 lb fast-setting
Gravel under the posts 3 × 50 lb bags (0.5 ft³)
Ticked items cost $366.17
More numbers
Post holes 27" deep, 10" across
Widest post spacing 7' 6" on center
Even gap between pickets 2 7/16" at a 2 1/2" gap
DrawingThe project drawn to scale. Left: 30' × 3' 6".30'3' 6"Left

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
Left 30' Add ×1 30 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.

9 × 50 lb fast-setting Bags 9 Left over 0.02 ft³ Weight 450 lb Cost $71.82 Reference price $7.98. Type your store's.

Shopping list

5 5 × 8 ft $67.60 Reference price $1.69. Type your store's.
65 65 × 4 ft $117.00 Reference price $0.45. Type your store's.
8 8 × 8 ft $38.40 Reference price $0.60. Type your store's.
2 2 × 1 lb box (126) $21.94 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.
5 5 × 4×4 caps $39.90 Reference price $7.98. Type your store's. Reference price $12.98. Type your store's.
9 9 × 50 lb fast-setting $71.82
3 3 × 50 lb bags (0.5 ft³) $16.44 Reference price $5.48. Type your store's.
Ticked items $366.17

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.

Left 30' 30 ft
Posts 4 bays in 1 runs: 3 line + 2 end + 0 corner + 0 gate 5 posts

Change:Widest post spacing, wood

How deep a post goes 0.5 × 42" out of the ground, or the frost depth 0" where deeper 21" + 6" = 27"

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

Posts, length 42" + 21" = 63" 5 × 8 ft
Concrete, each post (π ÷ 4 × 10" × 10" − 3 1/2" × 3 1/2") × 17 1/2" 0.671 ft³ × 5 = 3.357 ft³

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

Bags of concrete 3.357 ft³ ÷ 0.375 ft³ 8.95 → 9 × 50 lb fast-setting

Change:Yield, 50 lb fast-setting bag

Gravel under the posts π ÷ 4 × 10" × 10" × 6" × 5 1.364 ft³ → 3 × 50 lb bags (0.5 ft³)

Change:Gravel in the bottom of a hole

Rails 4 × 2 = 8 8 × 8 ft

Change:A rail every

Pickets, edge to edge (360" + 2 1/2") ÷ (3 1/2" + 2 1/2") 61 × 4 ft

Change:Gap between picketsGap under the pickets

With the waste for culls 61 × (1 + 5%) 64.05 → 65
Screws 61 pickets × 2 rails × 2 + 8 boards × 2 ends × 2 244 + 32

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

What it comes to 5 × 8 ft × $1.69/ft + 65 × 4 ft × $0.45/ft + 8 × 8 ft × $0.60/ft + 2 × $10.97 + 1 × $32.97 + 9 × $7.98 + 3 × $5.48 $366.17

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
Gap between picketsThe gap between pickets of a picket fence. Omni's fence FAQ works at 2½ in, Inch Calculator at 2 in; no maker read gives one. ~ 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 pickets a picket fence takes

Pickets with a gap between them are counted as pickets and gaps: n pickets and one gap fewer fill a run, so the count is (run + gap) ÷ (picket + gap), rounded up. A front-yard fence of two 30 foot runs either side of a 4 foot walk gate, in 1×4 pickets 3½ inches wide with 2½ inch gaps, takes (360 + 2.5) ÷ (3.5 + 2.5) = 60.4, so 61 pickets a run, and 9 on the gate: 131 pickets, 138 with 5% for culls. On a fence 3½ feet high each is a 4 foot picket set 2 inches off the ground.

Rounded up, the pickets will not land on exactly 2½ inches. Spread 61 of them evenly along 30 feet and the gaps come to (360 − 61 × 3.5) ÷ 60 = 2 7/16" — the width to cut a spacer block to, so the last picket meets the post as square as the first.

Rails, posts and the gate

A fence this low carries two rails a bay, top and bottom. Each 30 foot run is 4 bays of 7' 6", so 16 rails of 2×4, and 10 posts: 6 inside the runs, one at each end, and the two gate posts — 6×6, because a gate swings on them. The posts go 21 inches into the ground on 6 inches of gravel, half of what stands above it. The gate is framed from the same boards: two rails and a brace from the bottom of the hinge side to the top of the latch side, two hinges, and a latch.

Spacing

The gap is the Gap between pickets under Assumptions: 2½ inches is the figure Omni's fence FAQ uses, Inch Calculator uses 2. Narrow it and the count rises, widen it and it falls; the even gap on the page follows.

Round a pool the gap is not a matter of taste. Where the tops of the rails are less than 45 inches apart, as they are on any fence this height, the International Swimming Pool and Spa Code puts the rails on the pool side and holds the gaps to 1¾ inches (section 305.2.5); choose A pool under Assumptions and the page checks it. We are not connected with any maker, store or supplier named here.