Fence Calculator
Work out how many posts, rails and pickets you need for a fence from its length and post spacing. Example: 100 feet with posts every 8 feet needs 14 posts, 39 rails (3 per section) and 200 pickets.
Show steps
How to use the Fence Calculator
- Enter the total length of the fence run.
- Set the post spacing, usually 6 to 8 feet.
- Choose open run or closed loop, rails per section and picket size.
- Press Calculate for posts, rails and pickets.
Formula and method
Sections = length / post spacing (rounded up). Posts = sections + 1 for an open run, or sections for a closed loop. Rails = sections x rails per section. Pickets = length in inches / (picket width + gap), rounded up.
Worked example: 100 feet, 8 foot spacing
| Item | Count |
|---|---|
| Sections (100 / 8, rounded up) | 13 |
| Posts (13 + 1) | 14 |
| Rails (13 x 3) | 39 |
| Pickets (1,200 / 6) | 200 |
Posts needed by fence length at 8 foot spacing
| Length | Sections | Posts (open run) |
|---|---|---|
| 40 ft | 5 | 6 |
| 80 ft | 10 | 11 |
| 100 ft | 13 | 14 |
| 150 ft | 19 | 20 |
| 200 ft | 25 | 26 |
| 300 ft | 38 | 39 |
Choosing post spacing
Six to eight feet is standard for wood fences. Closer spacing makes a stiffer fence. Set posts about one third of their length in the ground, and check local rules for height and property lines before you build.
Frequently asked questions
How many fence posts do I need?
Divide the fence length by the post spacing, round up, and add 1 for an open run. 100 feet at 8 foot spacing needs 14 posts.
How many pickets do I need?
Convert the length to inches and divide by the picket width plus the gap. 100 feet with 5.5 inch pickets and 0.5 inch gaps needs 200.
How far apart should fence posts be?
Usually 6 to 8 feet center to center.
How many rails per section?
Two for fences up to about 4 feet tall, three for taller ones.
How much waste should I add?
About 5% for cuts and damaged boards.
Do gates change the count?
Yes. Add posts for the gate hardware and subtract the gate width from the picket length.
Sources
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