How to use the fence calculator
- Enter the total fence run from end to end in feet, then the number and width of gates. Gates are counted inside the run.
- Set the post spacing and rails per section to match your design, and add any corner posts. Tick the loop box if the fence closes on itself.
- Enter the picket width and the gap between pickets in inches. Use a gap of 0 for a solid fence.
- Read the posts, rails and pickets to buy. Optionally enter the concrete bags per post and prices for a materials estimate.
Formula
Fenced length = total run - (gates x gate width)
Fence sections = fenced length / post spacing, rounded up
Posts = fence sections + gates + 1 (open run), plus one per corner
Rails = fence sections x rails per section
Pickets = fenced length x 12 / (picket width + gap), then x (1 + waste), rounded up
In an open run, every section needs a post at each end and neighbors share posts, which is why you add one. A closed loop shares all posts, so that extra post is dropped.
Worked example: 100 feet of picket fence with one 4 foot gate
The fenced length is 100 - 4 = 96 ft. At 8 ft post spacing that is 96 / 8 = 12 sections, and the gate is a 13th opening, so there are 13 sections and 14 posts in an open run.
With 2 rails per section the fence needs 12 x 2 = 24 rails.
Each picket takes 5.5 + 0.5 = 6 inches, so 96 ft x 12 / 6 = 192 pickets. With a 10% allowance that is 211.2, so 212 pickets.
At 2 bags of concrete per post you need 14 x 2 = 28 bags. At $12 per post, $9 per rail, $2.50 per picket and $6.50 per bag the materials come to $1,096.00.
Post spacing and layout
A common starting point is a post every six to eight feet, but the right spacing depends on the rail material, the fence height, wind exposure and any panels you are using. If your panels are a fixed width, set the spacing to that width. When the run does not divide evenly, the last section is shorter, and the tool rounds up so you never end up a post short.
Corners add posts because the layout rarely lines up with the spacing at a turn. The tool adds one per corner, which is a deliberately simple and slightly generous assumption.
Gates
Each gate is counted as one opening between two posts, and the gate itself is excluded from the pickets and rails. Heavy gates often need larger or deeper posts and a stronger frame, which this tool does not size. Hinges, latches, drop rods and gate frames are separate purchases.
Concrete and setting posts
Setting posts in concrete is optional, since some fences use gravel or driven posts. The bags per post is therefore your own assumption, because it depends on hole diameter, depth, post size and the bag size. For a more detailed concrete estimate, use the concrete calculator with a round column. Local rules may also set a minimum post depth, especially in cold climates, so check before you dig.
Assumptions and limits
- Post spacing (8 ft) and rails per section (2) are editable assumptions, not rules.
- The fence is a straight run or a series of runs where each corner adds one extra post. Slopes and stepped sections are not modeled.
- Pickets are counted for one side only, and the waste allowance is applied to pickets, not to posts or rails.
- Concrete is optional and uses the bags per post that you enter. Clear the box to hide it.
- Hardware, bracing, caps, gravel, stain and permits are not included. Check local height limits and property line rules before building.
Frequently asked questions
How far apart should fence posts be?
Many fences use between 6 and 8 feet, but it depends on your rails or panels and your site. Set the spacing to your design value, since the tool does not choose it for you.
How many pickets do I need per foot of fence?
Divide 12 inches by the picket width plus the gap. At 5.5 inch pickets with a half inch gap that is 2 pickets per foot, and with no gap it is about 2.18.
Do I count gate posts separately?
The tool counts each gate as one opening between two posts, so the posts at both sides of the gate are included in the total. Heavy gates may need stronger posts, which you choose.
How many bags of concrete does each post need?
It varies with hole size, depth and the bag size. The tool starts at 2 bags per post as an editable assumption and lets you clear it. For a more careful figure, work out the hole volume with the concrete calculator.
What does the loop option do?
In a closed loop, such as a yard enclosure, every post is shared between two sections, so the extra end post is not needed. Leave it unchecked for a run with two ends.