Fence Calculator
Inputs
| Fence length | 30 m |
|---|---|
| Post spacing | 2.4 m |
| Rails per section | 2 rails per section |
| Picket width | 14 cm |
| Picket gap | 4 cm |
Fence Calculator
Estimate how many posts, rails, and pickets a wood fence needs from the total run length, post spacing, and picket dimensions.
Inputs
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Details
A 30 m fence needs about ... posts, ... rails, and ... pickets.
Fence
A wood fence is built from three repeating parts: vertical posts set in the ground, horizontal rails that span between posts, and pickets fixed to the rails to form the face. Each part is counted from the total fence length together with a couple of spacing choices, so the whole material list follows from a few simple ratios.
Posts and sections
A fence run is divided into sections, where one section is the span between two adjacent posts. The number of sections is the fence length divided by the post spacing, rounded up so a partial span still gets its own section:
sectionsposts=⌈spacinglength⌉=sections+1The extra post accounts for the fact that a straight run is capped at both ends: two sections need three posts, three sections need four, and so on.
Rails
Rails are the horizontal members that carry the pickets. Each section gets the same number of rails, so the total is simply the section count times the rails per section:
rails=sections×rails per sectionFences up to about 1.2 m4 ft use two rails; taller fences add a third in the middle to keep the pickets from bowing.
Pickets
Each picket takes up its own width plus one gap before the next one begins, so the repeat distance is the picket width plus the gap. Dividing the fence length by that repeat and rounding up gives the picket count:
pickets=⌈picket width+gaplength⌉A gap of zero produces a solid privacy fence and uses the most pickets for a given length.
Worked example
A 30 m100 ft fence with posts every 2.4 m8 ft, two rails per section, and 14 cm5.5 inch pickets set with a 4 cm1.5 inch gap:
So the run needs 14 posts, 26 rails, and 167172 pickets before any allowance for corners, gates, or waste.
What the estimate leaves out
This method covers a single straight run. Real fences add a post at every corner and on each side of a gate, and the picket count rises slightly if the boards do not divide evenly into the run. It is good practice to add a few percent for breakage and to confirm post spacing against local building code, which sometimes sets a maximum.
For another room-and-board material estimate, see the Drywall Calculator.
Frequently Asked Questions (FAQ)
How many fence posts do I need?
Divide the fence length by the post spacing and round up to get the number of sections, then add one. A straight run always needs one more post than it has sections because both ends must be capped. For a 30 m fence with posts every 2.4 m, that is 13 sections and 14 posts. Corners and gates require an extra post each, so add those separately.
Divide the fence length by the post spacing and round up to get the number of sections, then add one. A straight run always needs one more post than it has sections because both ends must be capped. For a 100 ft fence with posts every 8 ft, that is 13 sections and 14 posts. Corners and gates require an extra post each, so add those separately.
How many pickets does a fence need?
Each picket occupies its own width plus one gap, so the repeat distance is the picket width plus the gap. Dividing the fence length by that repeat and rounding up gives the picket count. For example, 14 cm pickets with a 4 cm gap repeat every 18 cm, so a 30 m fence needs about 167 pickets. A solid privacy fence (zero gap) uses more pickets for the same length.
Each picket occupies its own width plus one gap, so the repeat distance is the picket width plus the gap. Dividing the fence length by that repeat and rounding up gives the picket count. For example, 5.5 in pickets with a 1.5 in gap repeat every 7 in, so a 100 ft fence needs about 167 pickets. A solid privacy fence (zero gap) uses more pickets for the same length.
What is the standard post spacing for a wood fence?
The most common spacing for residential wood fences is 2.4 m on center, which balances material cost against rail strength. Spacing of 1.8 m is used where extra rigidity is wanted, such as on windy sites or for heavier panels. Wider than 2.4 m risks sagging rails. Always check local code, as some jurisdictions specify a maximum spacing.
The most common spacing for residential wood fences is 8 ft on center, which balances material cost against rail strength. Spacing of 6 ft is used where extra rigidity is wanted, such as on windy sites or for heavier panels. Wider than 8 ft risks sagging rails. Always check local code, as some jurisdictions specify a maximum spacing.
Disclaimer
This is a material estimate based on a single straight run. It does not add posts for corners, ends, or gates, nor allowance for waste, terrain, or panel layout. Confirm quantities against your final fence plan and add a margin for breakage.
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