Fence Calculator

Fence length, m

Post spacing, m

Fence height, m

Rows of rails

Effective sheet width, m

Result

Posts25
Bays24
Post length, m2.8
Rails, m120
Sheets55
Concrete for posts, m³1.25

There is always one more post than bay

Posts, bays, rails and sheets for a fence of any length, plus concrete for setting the posts.

Fence estimating starts with posts, and the off-by-one is easy: there is always one more post than there are bays. Sixty metres at 2.5 m spacing gives 24 bays and 25 posts, and forgetting the last one is common.

Post length matters too. About a third of the height goes into the ground, and never less than 800 mm, or frost heave will push the fence out of line over a winter. A two-metre fence wants posts of at least 2.8 m.

What this calculator shows

Posts and bays at your chosen spacing
Recommended post length including the buried section
Rail metres, sheet count and concrete volume

What to keep in mind

2.5 m spacing suits profiled sheet; use 2 m for heavy panels or exposed sites.
Concrete is allowed at 0.05 m³ per post — roughly a 250 mm hole a metre deep.

FAQs

What post spacing should I use?

2.5 m for profiled sheet and mesh, 2 m for heavy or ornamental panels and on exposed sites. Beyond three metres the rails start to sag.

How deep should posts go?

At least a third of the height and never under 800 mm. On heave-prone ground, go below the frost line or use screw piles.

How many rows of rails?

Two up to two metres, three above that. The top rail sits 250-300 mm below the top, the bottom one about 300 mm off the ground.

Concrete or compacted gravel?

On normal ground concrete is more reliable. On heave-prone clay, gravel works better because water drains away and frost cannot lift the post.

Worked example

A boundary fence

Input: 60 m, 2.5 m spacing, 2 m high, 2 rail rows, 1.1 m sheets

Output: 25 posts, 24 bays, 120 m of rail, 55 sheets

Note: Posts come out at 2.8 m: two metres above ground and 800 mm in concrete. Skimping on depth costs more to put right than it saves.

Useful links

All tools in Building & Repair

Fence Calculator

Result

Related tools

Concrete Calculator

Lumber Calculator

Square Footage Calculator

Useful links