Fence Post Spacing Calculator
Work out fence post spacing, post and rail counts, picket totals and concrete per hole for any run.
Enter your fence run and maximum spacing — the layout updates as you type.
- Sections (bays)
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- Posts needed
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- Actual spacing (on-center)
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- Clear gap between posts
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- Fenced length (minus gates)
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- Hole depth
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- Post length to buy
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- Rails
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- Pickets
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- Concrete per hole
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- Concrete total
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- Bags of mix
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Post positions along the fenced length (0)
Measured from the start of the fence, ignoring gate openings — add each gate width where you place it.
| Post | Distance from start |
|---|
Only the first 200 posts are listed here; the CSV download contains them all.
Estimates for planning and shopping lists. Always check your local building code for frost depth, maximum post spacing and setback rules before you dig, and call your utility locate service first.
How it works
The calculator uses the standard even-spacing method. It first subtracts the gate openings
from the total run to get the fenced length F, then divides that by the maximum
spacing you allow and rounds up:
sections = ceil(F ÷ max spacing). Rounding up guarantees no bay is ever wider
than your limit. The real on-center spacing is then F ÷ sections, and a straight
run needs sections + 1 posts, plus one extra post for every gate opening you drop
into the line. The clear gap you actually see between two posts is the on-center spacing minus
one post width.
Hole depth follows the common DIY rule of one third of the above-ground fence height, with a
2 ft (610 mm) minimum — override it in the box if your frost line is deeper. Concrete per hole
is the cylinder minus the buried post:
π/4 × diameter² × depth − post width² × depth. Bag counts assume an 80 lb bag of
concrete mix yields 0.60 cu ft, and a 25 kg bag yields 12.5 litres. Picket counts divide the
fenced length by the picket width plus one gap and round up.
Everything is plain arithmetic running in your browser — nothing you type is uploaded, stored or sent anywhere, and there are no ads or sign-ups.
Frequently asked questions
How far apart should fence posts be?
Most timber fences use 6 to 8 ft (1.8 to 2.4 m) on-center, and pre-made panels fix the spacing at the panel width. This calculator treats your figure as a maximum: it divides the fenced length by that limit and rounds the number of sections up, so the real on-center spacing always comes out at or below your maximum and every bay is identical.
How many posts do I need for my fence?
A straight run needs one more post than it has sections, so a 100 ft run at a maximum of 8 ft becomes 13 sections and 14 posts. Each gate opening adds one more post, because the gate is hung between its own pair of posts. The calculator subtracts the gate widths from the run before dividing and adds those extra posts for you.
How deep should a fence post go and how much concrete does each hole take?
The usual DIY rule is to bury one third of the above-ground fence height, with a 2 ft (610 mm) minimum — go deeper if your frost line is lower, using the override box. Concrete per hole is the hole cylinder minus the buried post: π/4 × diameter² × depth − post width² × depth. Bag counts assume 0.60 cu ft per 80 lb bag or 12.5 litres per 25 kg bag.