Work out fence post quantity instantly with clear inputs, formula shown and shareable results.
Post count is the number of spans plus one, because a fence needs a post at both ends of every run, with extra posts added at corners and either side of each gate. A typical 300 mm diameter hole 700 mm deep takes about 50 litres of concrete, so the total is straightforward once the count is known.
Post count
Posts = ceil(length / spacing) + 1 + corner posts + 2 per gate
Concrete
m³ = posts x 50 litres / 1000
Posts = ceil(length / spacing) + 1 + corner posts + 2 per gate. Post count is the number of spans plus one, because a fence needs a post at both ends of every run, with extra posts added at corners and either side of each gate.
It matches common panel and rail lengths and keeps rails from sagging. Closer spacing is needed for high fences or exposed sites where wind load governs.
This calculator takes 4 inputs: Fence length, Post spacing, Corner and end posts, Number of gates. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.