How it’s worked out
A panel fence alternates posts and panels, starting and ending with a post. A picket fence has posts at a spacing, rails between them and pickets along its length:
Panels = (length − post) ÷ (panel + post), rounded up Posts = panels + 1 Pickets = length ÷ (picket + gap), rounded up Post length = fence height + depth in the ground
Worked examples
20 m of 1.83 m panels with 100 mm posts needs 11 panels and 12 posts, each 2.4 m long for a 1.8 m fence set 0.6 m into the ground; the last panel is cut to about 0.5 m. A 100 ft picket fence with posts every 8 ft, 3 rails, 3½ in pickets and 1¼ in gaps needs 14 posts, 39 rails and 253 pickets.
How to read the result
- Panels and posts: the numbers to buy, including the cut panel at the end.
- Post length: the height of the fence plus what goes into the ground.
- Rails and pickets: with the bays spread evenly along the fence.
Common mistakes
- Forgetting the posts take up length: 11 panels of 1.83 m and 12 posts are more than 11 × 1.83 m.
- Setting posts too shallow: about a quarter of the post in the ground is the usual guide.
- Not allowing for gates: take their width off the length and add their posts.
How to use it
- Choose panels and posts, or rails and pickets.
- Type the fence length and the panel or picket sizes.
- Type the fence height and how deep the posts go, for the post length.
Questions
How many fence panels do I need?
Take one post width off the length, then divide by a panel plus a post and round up. 20 m of 1.83 m panels with 100 mm posts needs 11 panels.
How many posts for a fence?
One more than the number of panels, or one more than the number of bays on a picket fence.
How long should fence posts be?
The fence height plus about a quarter of the post in the ground: a 1.8 m (6 ft) fence usually takes 2.4 m (8 ft) posts.
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