How much fence material do I need?
Type the length of the fence line, the post spacing and your picket size. The fence calculator counts the posts, rails and pickets, and adds up the cost when you type prices.
- Posts
- 14
A 100 ft fence with posts 8 ft apart needs 14 posts, 39 rails and 230 pickets.
- Sections
- 13
- Rails
- 39
- Pickets
- 230
Posts: 14. A 100 ft fence with posts 8 ft apart needs 14 posts, 39 rails and 230 pickets.
How to calculate
Counts the posts, rails and pickets for a fence from its length, post spacing, rails per section and picket width and gap, with the material cost when you add prices.
Example with the default inputs (Fence length 100 ft, Post spacing 8 ft, Rails per section 3, Picket width 5.5 in, Gap between pickets 0 in, Extra pickets 5%): A 100 ft fence with posts 8 ft apart needs 14 posts, 39 rails and 230 pickets.
Method: Sections = ⌈length ÷ post spacing⌉; posts = sections + 1; rails = sections × rails per section; pickets = ⌈length × (1 + extra ÷ 100) ÷ (picket width + gap)⌉; cost = posts × post price + rails × rail price + pickets × picket price.
- One straight run with a post at each end. Each corner or gate adds posts; work out each straight side on its own and add them.
- Each rail spans one section, so buy rails at least as long as the post spacing.
- Defaults: posts 8 ft apart and 3 rails, as fence makers suggest for a 6 ft privacy fence (NMI Fence); 5½ in pickets (a 1×6 board) with no gap; 5% extra pickets.
Worked examples
Each example is checked against the calculator on every build.
- Fence length 100 ft, Post spacing 8 ft, Rails per section 3, Picket width 5.5 in, Gap between pickets 0 in, Extra pickets 0% gives Sections 13, Posts 14, Rails 39, Pickets 219.Source: NMI Fence, Fence Post Spacing Guide (privacy fence: posts 8 ft apart, 3 rails on fences 6 ft and taller; picket fence: 8 ft, 2 rails), https://nmifence.com/blog/fence-post-spacing; Extreme How-To, How To Build a Wood Fence (posts no wider apart than the rails, usually 6 to 8 ft on center), https://extremehowto.com/diy-privacy-fence/
- Fence length 96 ft, Post spacing 8 ft, Rails per section 2, Picket width 3.5 in, Gap between pickets 2.5 in, Extra pickets 0%, Price per post $12.00, Price per rail $6.50, Price per picket $2.25 gives Sections 12, Posts 13, Rails 24, Pickets 192, Material cost $744.00.Source: NMI Fence, Fence Post Spacing Guide (privacy fence: posts 8 ft apart, 3 rails on fences 6 ft and taller; picket fence: 8 ft, 2 rails), https://nmifence.com/blog/fence-post-spacing
- Fence length 98.43 ft, Post spacing 7.874 ft, Rails per section 3, Picket width 5.512 in, Gap between pickets 0.3937 in, Extra pickets 10% gives Sections 13, Posts 14, Rails 39, Pickets 220.Source: Extreme How-To, How To Build a Wood Fence (posts no wider apart than the rails, usually 6 to 8 ft on center), https://extremehowto.com/diy-privacy-fence/
How it works
For one straight run of fence:
- Sections = fence length ÷ post spacing, rounded up to a whole section.
- Posts = sections + 1 (a post at each end and between each pair of sections).
- Rails = sections × rails per section.
- Pickets = fence length × (1 + extra ÷ 100) ÷ (picket width + gap), rounded up to a whole picket.
- Material cost (when you type at least one price) = posts × post price + rails × rail price + pickets × picket price; an empty price counts as $0.
Units: 1 ft = 12 in = 0.3048 m exactly, 1 yd = 3 ft.
Rules. The fence length is from 0.1 m to 10,000 m; post spacing from 0.3 m to 5 m; picket width from 1 cm to 1 m; the gap from 0 to 1 m; rails per section a whole number from 0 to 6; extra from 0% to 100%; each price from $0 to $100,000.
Exact arithmetic. Each size is read as the exact decimal you typed, in the unit you typed it in, so 96 ft ÷ 8 ft is exactly 12 sections, never 13. When you type in a unit, the page stores the size in metres and reads it back as the decimal with the fewest significant digits, in one of the box's units, that gives the same stored number (a feet-and-inches pair counts by its value in inches; on a tie the first unit in the menu wins). Counts are rounded up from the exact quotient.
Output format. Posts, sections, rails and pickets are whole numbers. The cost shows dollars and cents, rounded half up from its exact value.
Assumptions
- Defaults: 100 ft of fence, posts 8 ft apart and 3 rails per section, as NMI Fence lists for a 6 ft privacy fence; 5½ in pickets (the actual width of a 1×6 board) with no gap; 5% extra pickets for cuts and bad boards.
- Each rail spans one section, so rails must be at least as long as the post spacing.
- Corners and gates are not counted: work out each straight side on its own and add the results (two sides that share a corner post need one post less).
Worked examples by hand
100 ft privacy fence, no extra. 100 ÷ 8 = 12.5, so 13 sections and 14 posts. Rails 13 × 3 = 39. Pickets 1,200 in ÷ 5.5 in = 218.2, so 219.
96 ft picket fence with prices. 96 ÷ 8 = 12 sections exactly; 13 posts; 12 × 2 = 24 rails. Pickets 1,152 in ÷ (3.5 + 2.5) in = 192. Cost 13 × $12 + 24 × $6.50 + 192 × $2.25 = 156 + 156 + 432 = $744.00.
30 m with 10% extra. 30 ÷ 2.4 = 12.5, so 13 sections, 14 posts, 39 rails. Pickets 30 × 1.1 ÷ (0.14 + 0.01) = 220 exactly.
Other questions people ask
How many fence posts do I need?
Divide the fence length by the post spacing, round up to whole sections, and add one post. 100 ft at 8 ft spacing is 12.5, so 13 sections and 14 posts. Each corner and gate needs its own posts, so work out each straight side on its own.
How far apart should fence posts be?
Usually 8 ft on centre for wood fences, the length of a standard rail board. Extreme How-To advises never spacing posts wider than the rails, usually 6 to 8 ft; NMI Fence suggests 6 to 8 ft for heavy board-on-board fences.
How many rails does a fence need?
NMI Fence suggests 2 rails per section for a 3 to 4 ft picket fence and 3 rails for a privacy fence 6 ft or taller. Rails = sections × rails per section, so 13 sections with 3 rails need 39 rails.
How many pickets do I need?
Divide the fence length by the picket width plus the gap, and round up. 100 ft is 1,200 in; 5½ in pickets with no gap need 1,200 ÷ 5.5 = 218.2, so 219 pickets, plus a few extra for cuts and split boards.
How much does a fence cost in materials?
Multiply each count by its price and add them up. A 96 ft picket fence with 13 posts at $12, 24 rails at $6.50 and 192 pickets at $2.25 costs $156 + $156 + $432 = $744 in posts, rails and pickets. Concrete, hardware and labour are extra.
Why is a 1×6 picket 5½ inches wide?
Lumber is named by its rough size before it is dried and planed. A board sold as 1×6 is about ¾ in thick and 5½ in wide, so type the actual width of your pickets.