Fence Calculator helps you calculate fence materials — free, instant, in your browser. Fill in Fence Length (m) and Post Spacing (m) on Fence and read your answer immediately. In Fence the working sits beside the answer. Fence works for one check or many. Nothing typed into Fence leaves your device or the tab. Fence is part of the Construction collection on CalcProMaster, alongside free fence calculator, free online fence calculator and more. Fence is great for comparing scenarios. Change one value and watch. Open Fence and enter your numbers.
What the defaults give
30 metres of fence at 2 metre post spacing needs 16 posts.
With two rails per bay that is 32 rails, and the run divides into 15 bays.
The formula
Bays = ceil(length ÷ spacing)
Posts = bays + 1
Rails = posts × 2
The plus one is what closes the run: posts sit at 0, 2, 4 … 30 metres, which is 16 positions. Rails are counted as two per post in this tool, a simple proxy for a two-rail fence; a three-rail fence needs posts × 3 and a panel fence is measured in panels rather than rails.
Worked examples
30 m at 2 m → 16 posts, 32 rails
20 m at 2 m → 11 posts, 22 rails
30 m at 2.5 m → 13 posts, 26 rails
50 m at 3 m → 18 posts, 36 rails
30 m at 1.5 m → 21 posts, 42 rails
100 m at 2.4 m → 43 posts, 86 rails
Choosing the spacing
Two metres is a common default for a garden or boundary fence in timber or light mesh. Closer spacing (1.5 m) stiffens a fence exposed to wind or carrying a heavy panel; wider spacing (3 m) suits stock fencing with strainers at the corners, where the wire carries the load and the posts only hold it in line.
Corners, ends and gate posts are not ordinary posts. A corner takes load from two directions and needs a brace; a gate needs a heavier post set deeper, often 100 mm or 125 mm rather than 75 mm. Add those separately — the formula treats every post as identical.
What the count does not cover
Concrete is usually the biggest hidden line: roughly one 20 kg bag per post hole at 2 m spacing, so 16 bags at the defaults. Then fixings, nails or clips, a gravel board if the fence sits on soil, and stain or treatment for the timber.
Depth matters more than count. A post should be set about a third of its length in the ground — 600 mm for a 1.8 m post — and deeper on soft ground or an exposed site. A fence that fails usually fails at the posts, not at the rails, so spending on deeper holes and better concrete is cheaper than rebuilding in three years. Check boundary rules and height limits before ordering, since permitted development caps fence height in many jurisdictions.
Frequently Asked Questions
How many posts for a 30 metre fence?
Sixteen at 2 metre spacing: 15 bays plus one post to close the run. That gives 32 rails at two per post.
Why is there always one more post than bays?
Because posts mark both ends of every bay. Fifteen bays need a post at each division, which is sixteen positions in total.
How much concrete do I need?
Roughly one 20 kg bag per post hole at 2 metre spacing, so about 16 bags for a 30 metre run. Corners and gate posts take more.
What post spacing should I use?
Two metres for typical garden fencing, 1.5 metres for exposed or heavy panel fences, and up to 3 metres for stock wire with braced strainers at the corners.
Does the calculator include gate posts?
No. It treats every post as identical. A gate needs a heavier post set deeper, and corners need bracing, both added on top of the count.
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