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Wire and Farm Fence Calculator

Barb spacing from ASTM F1665. Post spacing is yours, and this says why

A wire fence is held up by its corners. The line posts only keep the wire off the ground; every pound of tension in every strand ends up in the end and corner assemblies, and an unbraced corner leans, then pulls out, then takes the fence with it. This counts the wire and the posts, and it counts the braces too.

Wire fence takeoff

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Barb spacing is the ASTM F1665 figure. Post spacing is an input, because no equivalent standard was found for farm wire.

Specification summary

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

Entered

Result

Line posts, strands and the corner that does the work

Worked example

A quarter mile of five strand barbed wire, T-posts at 12 ft, an end post at each end, no corners.

  1. Posts. 1,320 ft at 12 ft is 109 line posts plus 2 ends, so 111 in total.
  2. Wire. 5 strands × 1,320 ft = 6,600 ft, which is exactly 5 rolls.
  3. Barbs. At the ASTM F1665 5 in spacing that is 15,840 barbs, which is a number nobody needs but explains the weight.
  4. Clips. One per strand per post is 555 clips.
  5. Braces. 2 assemblies, and they are the only reason the other 109 posts stay upright.

The brace line is deliberately last and deliberately blunt. Most people costing a wire fence count posts and wire and forget that each end needs a horizontal rail and a diagonal tension wire to work at all.

The formula

Counting, with one term people leave out:

posts = ⌈ L / s ⌉ − 1 + terminals    wire = L × n    clips = posts × n
L
total run, ft
s
line post spacing, ft
n
strands
terminals
end and corner posts, each of which needs a braced assembly
barbs
wire footage × 12 / barb spacing. 5 in per ASTM F1665 four point

Wire is sold in 1,320 ft rolls, a quarter mile, which is why fencing is costed per rod and per roll rather than per foot in most of the country.

What is published here and what is not

Chain link has a manufacturers' institute that publishes post spacing and footing depth. Vinyl has a wind table. Farm wire fencing has neither, and this page says so rather than inventing a figure.

What is published is the barb. ASTM F1665 specifies four point barbed wire with barbs at 5 in on centre, and the CLFMI product manual quotes it directly when specifying barbed wire above a chain link fence. Three inch spacing is also sold, so read the label.

Line post spacing is a tension and terrain question. Common practice runs 8 to 16 ft, tighter on slopes, at dips and near corners, and it is genuinely a judgement rather than a specification. The calculator takes yours.

The part worth spending the words on is bracing. An H-brace or a double H at every end and corner is what resists the pull of the strands. It is the single most skipped item in a wire fence budget and the single most common reason a fence needs redoing in five years.

Why the corner is the whole fence

Tension in a wire fence has to end somewhere. Every strand you stretch pulls on the terminal post at each end, and on a five strand fence at working tension that is a substantial and permanent horizontal load applied near the top of a post set in soil.

A single post cannot take it. It rotates in the ground, the top comes toward the fence, the wire slackens, and the failure is progressive. The answer is a brace assembly: a second post set back, a horizontal rail between them near the top, and a diagonal tension wire from the top of the terminal post to the bottom of the brace post, twisted tight.

That geometry converts the pull into compression in the rail and tension in the diagonal, both of which the assembly can take. It is the oldest piece of structural engineering on a farm and it is why fences built in 1950 are still standing.

T-posts, wood posts and what each is for

Steel T-posts are line posts. They drive fast, they are cheap, and they are not terminal posts: they cannot be braced and they will bend under end tension. Every end, corner, gate and significant change of direction wants a wood post.

Wood line posts cost more and are worth it on rough ground, at the bottom of dips where the fence wants to lift, and anywhere stock lean on it.

The clip counts above assume one clip per strand per post, which is standard for T-posts. Wood posts take staples, and the convention is to leave them slightly loose so the wire can move rather than being pinched.

Check your local rules before buying barbed wire

Barbed wire is restricted or outright prohibited in residential zones in a great many municipalities, and where it is permitted there are often rules about minimum height, which side the barbs face and proximity to a footpath.

This is entirely local and nothing on this page speaks to it. If the fence is anywhere near a residential boundary, ask before you order.

For a residential boundary the privacy fence calculator or the chain link calculator are the relevant pages, and both have published standards behind them.

Frequently asked questions

How far apart should T-posts be?
Commonly 8 to 16 ft, closer on slopes, in dips and near corners. Unlike chain link, which the CLFMI manual caps at 10 ft on centre, no equivalent published standard was found for farm wire fencing, so it is a tension and terrain judgement rather than a specification.
How much barbed wire do I need?
Run length times strands. A quarter mile of five strand is 6,600 ft, which is exactly five 1,320 ft rolls. Wire is sold by the quarter mile roll, which is where fencing by the rod comes from.
What is the barb spacing on barbed wire?
ASTM F1665 specifies four point barbed wire with barbs at 5 in on centre, quoted in the CLFMI product manual. Three inch spacing is also sold, so read the label rather than assuming.
Do I need a brace at every corner?
Yes, and at every end and gate. All the tension in every strand terminates there. A single unbraced post rotates in the ground, the wire slackens and the failure spreads along the fence.
Can I use T-posts for corners?
No. T-posts are line posts. They cannot be braced and they bend under end tension. Corners, ends, gates and significant direction changes want wood posts in a braced assembly.
How many clips do I need?
One per strand per post. A five strand fence with 111 posts is 555 clips. Wood posts take staples instead, left slightly loose so the wire can move rather than being pinched.
Is barbed wire legal in a residential area?
Often not. It is restricted or prohibited in many residential zones, and where permitted there are frequently rules on height and barb orientation. It is entirely local, so ask your municipality before ordering.

Check these numbers yourself

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 2026-09-08. Codes are amended locally; confirm against the edition your jurisdiction enforces.

Related calculators

Post spacing here is yours, not a standard. No published spacing specification for farm wire fencing was found, unlike chain link and vinyl. Brace assemblies are not optional. Barbed wire is restricted or prohibited in many residential zones and that is a local rule this page cannot know.