How far apart are split rail fence posts?

The rail length less the seating depth at each end. With 10 ft rails seating 4 in into each post that is 9 ft 4 in, not 10 ft. Measure your own rails and mortises, because both vary by mill.

How many rails do I need for a split rail fence?

Two or three per section depending on the style. A 100 ft run in 10 ft rails is 11 sections, so 22 rails for a two-rail fence and 33 for a three-rail.

How deep should split rail fence posts be?

Commonly 24 to 30 in, deeper where frost demands it. Frost depth is local and this page will not publish one number for it. Depth also has to suit the post length you buy.

Do split rail posts need concrete?

Line posts traditionally do not. They are tamped with soil and gravel so the fence can be reset as the ground moves, which split rail does. Gate posts are the exception and are normally set in concrete.

What length posts do I need?

The hole depth plus the height above ground. A two-rail fence 3 ft 6 in tall with posts 30 in deep needs 6 ft posts. Three-rail fences are taller and need longer posts.

Is there a standard for split rail fencing?

No, not in the way chain link and vinyl have published manufacturer standards. It is a sawn product and dimensions vary between mills, which is why this calculator works from the rail you are buying rather than from a published figure.

How much does a split rail fence cost?

HomeGuide published $15 to $35 per linear foot installed. That is somebody else's national range, attributed and dated on the fence cost page, not a figure this site sets.

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Split Rail Fence Calculator

Arithmetic from your rail length. There is no published standard here

Split rail is the one fence where you do not choose the post spacing. The rails seat into mortises cut in the posts, so the centres are the rail length less however far each end goes in. Buy 10 ft rails and your posts land at about 9 ft 4 in, and no amount of planning changes that.

Split rail takeoff

Total run

Rail length

Rails per section

Hole depth

Hole diameter

End posts

no.

Corner posts

no.

Gate openings

no.

Everything here derives from your rail length. Measure a rail and a mortise before setting out.

Specification summary

Generated from on . Reopen that address to reproduce these figures exactly.

Entered

Result

Privacy fence elevation

Worked example

A 100 ft run of two-rail split rail using 10 ft rails, holes 30 in deep and 10 in wide.

Centres. A 10 ft rail seating 4 in into each post gives 9 ft 4 in centres, not 10 ft.
Sections. 100 ft at 112 in is 11 sections, so 12 posts.
Rails. Two per section is 22 rails and 44 mortises.
Post length. 30 in in the ground plus 3 ft 6 in above it means posts at least 6 ft long.
Backfill. Soil and gravel, not concrete, on the line posts. Only the gate posts get concrete.

The 8 in you lose to the mortises is the whole point. Set your posts at a true 10 ft and the rails will not reach, which is discovered at post nine.

The formula

One subtraction that everything else follows from:

centre = 12r − 2m sections = ⌈ 12L / centre ⌉ posts = sections + 1 + corners

r: rail length, ft, as supplied
m: how far each rail end seats into the post, in. 4 in is common
L: total run, ft
corners: each corner needs its own post, and the run restarts from it

The seating depth is the term to measure rather than assume. Mortise depth varies between mills, and a 1 in error over eleven sections is nearly a foot by the end of the run.

Why this page publishes no specification

Chain link has the CLFMI product manual. Vinyl has a manufacturer's wind table. Split rail has neither, because it is a sawn timber product made by many mills with real variation in rail length, mortise depth and post section.

So this page does arithmetic from the rail you are actually buying rather than publishing a spacing and calling it standard. The 4 in seating depth in the default is a common figure and it is a default, not a specification.

The one thing worth stating firmly is the direction of the error. Post centres are always shorter than the rail, never longer, and setting out at the nominal rail length is the mistake that shows up nine posts in when the rails stop reaching.

Line posts are traditionally tamped with soil and gravel rather than concreted, so a split rail fence can be reset as the ground moves. Gate posts are the exception. That is convention rather than code, and it is why the backfill line here says backfill rather than concrete.

Frequently asked questions

How far apart are split rail fence posts?: The rail length less the seating depth at each end. With 10 ft rails seating 4 in into each post that is 9 ft 4 in, not 10 ft. Measure your own rails and mortises, because both vary by mill.
How many rails do I need for a split rail fence?: Two or three per section depending on the style. A 100 ft run in 10 ft rails is 11 sections, so 22 rails for a two-rail fence and 33 for a three-rail.
How deep should split rail fence posts be?: Commonly 24 to 30 in, deeper where frost demands it. Frost depth is local and this page will not publish one number for it. Depth also has to suit the post length you buy.
Do split rail posts need concrete?: Line posts traditionally do not. They are tamped with soil and gravel so the fence can be reset as the ground moves, which split rail does. Gate posts are the exception and are normally set in concrete.
What length posts do I need?: The hole depth plus the height above ground. A two-rail fence 3 ft 6 in tall with posts 30 in deep needs 6 ft posts. Three-rail fences are taller and need longer posts.
Is there a standard for split rail fencing?: No, not in the way chain link and vinyl have published manufacturer standards. It is a sawn product and dimensions vary between mills, which is why this calculator works from the rail you are buying rather than from a published figure.
How much does a split rail fence cost?: HomeGuide published $15 to $35 per linear foot installed. That is somebody else's national range, attributed and dated on the fence cost page, not a figure this site sets.

Check these numbers yourself

ASTM F567, Standard Practice for Installation of Chain-Link FenceCited for contrast: chain link has a published installation standard and split rail does not.
HomeGuide, how much does a wood fence costWritten by Sarah Noel, published 22 December 2025. Split rail installed cost range, quoted on the fence cost page.

How every figure here is verified: Sources & Method. Who builds this: About. Found something wrong? Tell us and it gets fixed or removed.

Figures on this page last checked against the source documents on 2026-09-07. Codes are amended locally; confirm against the edition your jurisdiction enforces.

Related calculators

No published standard exists for split rail. Every figure here derives from the rail length and seating depth you enter, and both vary between mills. Measure what you are buying. Hole depth must suit your local frost line.