Fence Calculator
Plan a complete fence run from its length, post spacing and height. Get the number of posts, sections, rails and pickets, the post length and the concrete each footing needs, plus an optional material cost estimate. Works in feet or metres.
Formula
Worked example
A 100 ft run with 8 ft spacing: ceil(100 / 8) = 13 sections, so 13 + 1 = 14 posts. With 3 rails each that is 39 rails. Facing it with 5.5 in solid pickets needs ceil(100 / (5.5/12)) = 219 pickets. A 6 ft fence uses 9 ft posts, with about 2 ft buried, and roughly 1 to 2 bags of concrete per hole.
How to calculate fence posts and sections
Divide the total fence length by the post spacing and round up to find how many sections (panels) the run contains, since a partial gap still needs its own full section. The number of posts is the number of sections plus one, because both ends of a straight run need a post. For example, a 100 foot fence with 8 foot spacing has 13 sections and 14 posts once you round the half section up. Add one extra post for every corner, gate or change in direction, since those fall outside the straight run.
Counting rails and pickets
Rails are the horizontal members that span between posts and carry the boards. Low fences use two rails per section, while taller privacy fences use three for stiffness, so multiply rails per section by the number of sections. To count pickets, divide the run by the combined width of one picket plus the gap you want between pickets. A solid privacy fence uses a zero gap, while a spaced picket or ranch look uses a wider gap. Always round the picket count up and buy a few spares for cuts and waste.
Post length and concrete footings
A common rule sets the post length at 1.5 times the fence height, so about one third of each post sits below ground for stability. The buried part is set in a concrete footing whose hole is usually about three times the width of the post. The concrete needed per hole is the hole volume minus the volume the post takes up, and the calculator totals this across every post and converts it to standard 60 pound (27 kg) bags, each yielding roughly 0.45 cubic feet. Always set posts below the local frost line so the ground cannot heave them.
Estimating the cost
Turn on the cost estimate to price the four main materials: posts, rails, pickets and concrete bags. Enter your local price for each and the calculator multiplies it by the quantities it worked out, then sums them into a single planning figure in your chosen currency. Real quotes vary with timber grade, hardware, gates and labour, so treat the total as a materials budget rather than a fixed price, and confirm quantities against your site before you order.
Posts needed by length and spacing
| Length | 6 ft spacing | 8 ft spacing | 10 ft spacing |
|---|---|---|---|
| 50 ft | 10 | 8 | 6 |
| 100 ft | 18 | 14 | 11 |
| 150 ft | 26 | 20 | 16 |
| 200 ft | 35 | 26 | 21 |
| 300 ft | 51 | 39 | 31 |
Posts for a straight run (includes both end posts). Sections = posts - 1.
Frequently asked questions
Why is the number of posts one more than the number of sections?
Each fence section sits between two posts, and consecutive sections share a post. A run of N sections therefore needs N + 1 posts: one at the start, one at the end, and a shared post between every neighbouring pair of sections. Corners and gates add further posts on top of that.
How many pickets do I need?
Divide the fence length by the width of one picket plus the gap between pickets, then round up. For a solid privacy fence the gap is zero, so a 100 ft run with 5.5 in pickets needs about 219 boards. A spaced picket look with a 2 in gap on the same run needs far fewer. This calculator does the math once you enter the picket width and gap.
How long should fence posts be and how much concrete per post?
A good rule is a post length of 1.5 times the fence height, burying about one third of it. For a 6 ft fence that is a 9 ft post set roughly 2 to 3 ft deep. The concrete per hole is the hole volume minus the post, and a hole about three times the post width usually needs one to two 60 lb bags per post. The calculator totals the bags for you.
Does this include posts for corners and gates?
The straight run math gives sections + 1 posts. Use the extra posts field to add one post for each corner, gate opening or change in direction, and the totals, rails and concrete update to match.