How many fence posts do I need?

A fence run always needs one more post than it has bays. Divide the run length by the panel width and round up to get the bays, then add one for the posts.

How deep should fence posts go?

Set posts at least 600 mm into the ground, or roughly a quarter to a third of the above-ground height. Taller fences and exposed, windy sites need deeper, wider holes.

How much postcrete per post?

Two bags per post suits a standard fence post in a typical hole. Larger posts, deeper holes or heavy gate posts need more, so adjust the bags-per-post figure.

What is the Fence Post Calculator?

Calculate how many fence posts and panels a run needs from the total length and panel width, plus the postcrete bags to set the posts. Runs in your browser. It runs free in your browser on Gera Tools, with nothing uploaded.

Fence Post Calculator

Name: Fence Post Calculator
Creator: Gera Tools
License: https://creativecommons.org/licenses/by/4.0/

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A run of fencing is a line of bays, each holding one panel, with posts between and at both ends. The key fact is that there is always one more post than there are bays. This calculator applies that to your run length.

How it works

bays   = ceil(fence length / panel width)
posts  = bays + 1
panels = bays
bags   = posts × postcrete bags per post

Because you need a post at both ends of the run as well as between every panel, the post count is always one greater than the bay count.

Worked example

A 20 m fence with 1.83 m panels, two bags of postcrete per post:

Bays = ceil(20 / 1.83) = 11
Posts = 11 + 1 = 12
Panels = 11
Postcrete = 12 × 2 = 24 bags

What to watch

Gates take the place of a panel. If the run includes a gate, count its opening as one bay and buy the gate and its heavier posts separately.

Depth and wind. Set posts at least 600 mm deep, and go deeper with wider holes for tall fences or exposed sites — most fence failures start with posts that were not set firmly enough.