Planning permission
In England and Wales a fence over 2 m (1 m where it borders a highway or footpath) normally needs planning permission. Check permitted development rules for your address.
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Fence calculator
Work out every post, panel, pale and bag of concrete before you buy. Dimensions, units and prices default to your region — change anything you like.
UK Showing United Kingdom standards: metric units and GBP pricing.
Layout preview
Post
Bay
Schematic of the run, not to scale. Gate openings are shown in place.
Before you dig
Whose boundary is it?
You need permission from the landowner before building on a boundary. Deeds and Land Registry plans show who owns the fence line.
Frost depth
Southern states can get away with 18–30 in holes; northern states and Canada need 36–48 in. Posts that sit above the frost line heave every winter.
How the numbers are worked out
Everything on this page comes from these five steps. Change the inputs and the maths follows.
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1
Runs and posts
A gate splits the line into separate runs. Each run is divided into bays no wider than the post spacing, rounded up, so posts = runs × (bays + 1). The real spacing is the run length divided by the number of bays.
posts = runs × (bays + 1) -
2
Concrete
Hole volume = π/4 × diameter² × depth. The post footprint is subtracted, and the remainder is multiplied by the number of posts, then divided by the yield of one bag and rounded up.
V = π/4 · d² · h − post -
3
Counting the boards
Per bay: (bay length − pale width) ÷ (pale width + gap), rounded down, plus one. That guarantees no gap is wider than the one you asked for.
⌊(bay − w) ÷ (w + gap)⌋ + 1 -
4
Cost
Each material quantity is multiplied by the unit price you see in the form. Waste allowance is applied to boards and screws because those are the items that get cut and dropped.
total = Σ qty × unit price
Fence calculator questions
How many posts do I need for a 100 ft fence?
With posts at 8 ft centres a straight 100 ft run needs 14 posts: 12 full 8 ft bays plus one 4 ft closing bay. The calculator reports the exact figure for your spacing, and adds the posts either side of each gate.
How much concrete does one fence post need?
A 10 in hole 30 in deep takes about two 80 lb bags once the 4x4 post is in place. Wider augers or deeper holes need proportionally more — the calculator works out the volume and rounds up to whole bags.
What is the standard fence post spacing?
8 ft (2.4 m) centres for panels and paling fences; 6 ft (1.8 m) for heavy closeboard panels or exposed, windy sites. Never exceed the panel width or you will be cutting panels down.
How many pickets or palings do I need?
Divide the bay length by the pale width plus the gap, round down, then add one. An 8 ft bay with 3.5 in pales and a 0.5 in gap works out at 24 pales per bay.
How accurate is the cost estimate?
It uses typical retail prices for your region, and every price is editable. It covers materials only: labour, removing the old fence and disposal are separate.
Do I need permission to build a fence?
In England and Wales a fence over 2 m, or over 1 m next to a highway, usually needs planning permission. In the US and Canada the rules come from the municipality or HOA. In Australia and New Zealand check state or council rules, and always confirm who owns the boundary first.