Fence Calculator
Posts, rails, and pickets for a perimeter.
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Formula
posts = ceil(perimeter ÷ spacing) + 1; rail length = perimeter × rails × (1 + waste%)
Posts are spaced along the perimeter plus a closing post. Rail lumber is perimeter times number of horizontal rails, with waste. Pickets assume ~10 cm on-centre spacing.
Worked example
40 m perimeter with posts every 2.4 m needs 18 posts. Three rail courses need about 126 m of rail stock (with 5% waste) and roughly 400 pickets at 10 cm spacing.
Where this can give the wrong answer
- Corners and gates need extra posts — spacing math may undercount; add posts manually.
- Picket count is sensitive to gap width — adjust if you use 5 cm or 15 cm gaps.
- Sloped ground changes post height, not count along a level perimeter.
FAQ
- Often ⅓ of above-ground height in concrete — not calculated here. Heavier fences need deeper footings.