A fence is arithmetic you can see from the road: pickets, posts and rails multiplied along a line. Counting them correctly before you buy is the difference between one trip to the lumberyard and three.
Pickets: width plus gap
Each picket occupies its own width plus the gap that follows it. Divide the run by that combined unit and round up — the most common mistake is dividing by the picket width alone and coming up short.
Posts: the skeleton
Posts carry the load and set the fence's rhythm. Standard spacing of 2–2.4 m keeps rails stiff and the whole structure true. Add one post for the starting end, and more wherever the run turns a corner.
Rails and the long game
Rails tie it together — two for a low picket fence, three for height. Timber wants treating, and posts want concrete; both are cheap compared with redoing a sagging fence a few years early.
Frequently asked questions
Divide the fence length by the width of one picket plus the gap between them, then round up. A 10 m fence with 10 cm pickets and 5 cm gaps needs 67 pickets.
2–2.4 m (6–8 ft) is standard. Closer spacing is sturdier and allows thinner rails; wider spacing makes the fence sag.
About a 20 kg bag of post mix per hole is a common guide — enough to anchor the post and resist wind load.