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Fence Post Spacing Calculator

Each run in even bays, none wider than you allow — the spacing to mark out and the posts it takes.

An estimate — mark the first and last posts, then measure the bays between them.

200' · 2400 in · 200 ft · 60.96 m

200 ft

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

Answer

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Widest post spacing

10' on center

200 ft of fence · 20 bays · 21 posts in holes 36" deep

Posts 21 posts
Rails 60 rails · 3 a bay
Fence, gates left out 200 ft
Concrete 46 × 50 lb fast-setting
Gravel under the posts 12 × 50 lb bags (0.5 ft³)
Ticked items cost $1,459.17
More numbers
Post holes 36" deep, 10" across
DrawingThe project drawn to scale. Run 1: 200' × 4'.200'4'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.
Buying noteSplit rail makers say to tamp the posts in earth, not to set them in concrete (West Virginia Split Rail), so the concrete and gravel rows start unticked. Tick them if you set yours in concrete.

Breakdown

Run or gate Measurements Qty Length Share
Run 1 200' Add ×1 200 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.
Buying noteSplit rail makers say to tamp the posts in earth, not to set them in concrete (West Virginia Split Rail), so the concrete and gravel rows start unticked. Tick them if you set yours in concrete.

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.

46 × 50 lb fast-setting Bags 46 Left over 0.01 ft³ Weight 2,300 lb Cost $367.08 Reference price $7.98. Type your store's.

Shopping list

19 19 × 7 ft $360.43 Reference price $2.71. Type your store's.
2 2 × 7 ft $37.94 Reference price $2.71. Type your store's.
60 rails $1,060.80 Reference price $17.68. Type your store's.
46 46 × 50 lb fast-setting $367.08
12 12 × 50 lb bags (0.5 ft³) $65.76 Reference price $5.48. Type your store's.
Ticked items $1,459.17

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.

Run 1 200' 200 ft
Posts 20 bays in 1 runs: 19 line + 2 end + 0 corner + 0 gate 21 posts

Change:Post spacing, split rail

How deep a post goes 30" in the ground, or the frost depth 0" where deeper 30" + 6" = 36"

Change:Split rail post in the groundYour frost depthGravel in the bottom of a hole

Line posts, length 48" + 30" = 78" 19 × 7 ft
End posts, length 48" + 30" = 78" 2 × 7 ft
Concrete, each line post (π ÷ 4 × 10" × 10" − 5" × 5") × 26 1/2" 0.821 ft³ × 19 = 15.6 ft³

Change:Split rail post, acrossHole across, split rail postConcrete stops under the ground

Concrete, each end post (π ÷ 4 × 10" × 10" − 5" × 5") × 26 1/2" 0.821 ft³ × 2 = 1.642 ft³

Change:Split rail post, acrossHole across, split rail postConcrete stops under the ground

Bags of concrete 17.242 ft³ ÷ 0.375 ft³ 45.98 → 46 × 50 lb fast-setting

Change:Yield, 50 lb fast-setting bag

Gravel under the posts π ÷ 4 × 10" × 10" × 6" × 19 + π ÷ 4 × 10" × 10" × 6" × 2 5.727 ft³ → 12 × 50 lb bags (0.5 ft³)

Change:Gravel in the bottom of a hole

Split rails 20 × 3 60

Change:A split rail every

What it comes to 19 × 7 ft × $2.71/ft + 2 × 7 ft × $2.71/ft + 60 × $17.68 $1,459.17

Assumptions

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

Assumption Value Confidence
Post spacing, split railWest Virginia Split Rail installation instructions: 11 ft rails lapped 6 in into each post, so posts stand about 10 ft 3 in on center. in From a data sheet or an agency document
A split rail everySplit rail is sold two rails for a fence about 3 ft high and three for about 4 ft; one rail for every 18 in of height gives the same. ~ in Derived or single-supplier
Split rail post in the groundWest Virginia Split Rail: post holes 24-30 in deep, backfilled with tamped earth. The deep end, which puts a 3-rail fence on a 7 ft post. in 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
Split rail post, acrossA split rail post is a split log about 5 in across; taken as square for the hole it fills. ~ in Derived or single-supplier
Hole across, split rail postA split rail post's hole; the rail maker gives a depth and no width. ~ 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 far apart to set fence posts

Divide each run into equal bays no wider than the spacing you allow, and the bays round up. 100 feet at no more than 8 feet is 12½ bays, so 13 bays of 7' 8 5/16" on center, and 14 posts. Thirteen bays of 8 feet would overshoot by 4 feet; twelve would leave one bay 4 feet wider than the rest. Even bays put every rail on the same cut and every post the same distance from the next.

RunBays at 8 ft or lessOn centerPosts
50 ft77' 1 11/16"8
60 ft87' 6"9
75 ft107' 6"11
100 ft137' 8 5/16"14
150 ft197' 10 3/4"20

Which spacing

A wood fence on 2×4 rails is set no more than 8 feet apart, the length of the rail that spans a bay; wider than that a rail sags under the pickets, which is what builders say and what Inch Calculator and Omni both use — no standard gives the figure. Chain link line posts may be 10 feet apart. A panel fence has no choice: its posts stand a panel apart, 96 inches for an 8 foot vinyl or wood panel and 72½ for a 6 foot aluminum one. Split rail stands a rail apart, about 10 feet 3 inches for an 11 foot rail. Each is a figure under Assumptions you can change.

Several runs

Every run is divided on its own, from corner to corner or from end to gate, because a corner post is where both runs stop. A back yard of 50, 100 and 50 feet is 7, 13 and 7 bays — 27 — and 28 posts, the corners counted once.

Marking it out

Set the end and corner posts first and pull a string between them at post height. Measure the on-center spacing along the string from one end, mark each post, and dig. Measuring each bay from the last post adds up its errors; measure every mark from the same end. For the gaps between pickets — the even spacing a spacer block is cut to — use the picket fence calculator. We are not connected with any maker, store or supplier named here.