Estimate linear footage, post counts, post-hole concrete, and rails with unit and wastage controls.
How this is calculated
Fenced length is the perimeter minus gate openings, divided by post spacing for sections, plus one for the closing post.
fence_length = (perimeter − gate_widths) × (1 + wastage%)sections = ceil( fence_length ÷ spacing )posts = sections + 1rails = sections × rails_per_sectionconcrete_bags = ceil( π × (hole_diameter/2)² × hole_depth × posts ÷ cu_ft_per_bag )Set hole depth to your local frost line for permanent posts (≈ 36–48″ in southern Ontario).
60 lb bags yield ≈ 0.45 cu ft, 80 lb bags ≈ 0.6 cu ft.
Rails estimate counts sections × rails-per-section. Gate panel rails and heavier hardware-rated gate posts are excluded; add ≈ 2 rails and 2 post upgrades per gate for contractor-grade material lists.
How deep should fence post holes be?
Below your local frost line, 36–48″ in southern Ontario, deeper further north. Shallower holes will heave with frost cycles and pull the fence out of plumb within a couple of seasons.
What's the right post spacing?
6–8 ft is typical for residential wood fences. Pre-fab panels usually dictate spacing; for custom builds, shorter spacing means more posts but stiffer panels and easier hardware sourcing.
Do I need a building permit for a fence?
Often, yes; most municipalities have height limits (typically 6 ft side/rear, 4 ft front) and may require a permit above those. Pool fencing has its own stricter requirements. Check before you dig.
Posts and sections for a fence line
If you are quoting a fence or buying material for your own yard, you need three counts that hang together: sections, posts, and the concrete to set them. Miss the post count by one and you are back at the yard mid-build.
A worked example
Take a backyard that measures 100 ft by 60 ft, so 320 feet around. Subtract a 4-foot walk gate and a 10-foot drive gate, 14 feet of openings, and you have 306 feet of fence. At 8-foot spacing, 306 divided by 8 is 38.25, which rounds up to 39 sections. Posts always come to sections plus one, so 40 line posts, before you add the heavier posts each gate needs. For setting them to a 42-inch frost depth, figure roughly 2 cubic feet of concrete per hole. Forty holes is about 80 cubic feet, or close to 130 bags of 80-pound mix.
Common mistakes
- Setting posts above the frost line. In southern Ontario the frost line runs 36 to 48 inches, and a post set shallow will heave and lean a little more every winter.
- Counting one post per section. You always need one extra: a three-section run takes four posts, not three.
- Treating gate posts like line posts. A gate post carries the weight and the swing, so it usually wants a bigger hole and more concrete than the posts on either side of it.
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