Fence Calculator
Enter the fence length and post spacing to get posts, rails, pickets and concrete.
What is calculated
- Posts: length ÷ spacing, plus one. A 2.5 m spacing balances cost and stiffness; in windy areas profiled sheet needs 2–2.5 m.
- Rails: length × number of rows. Two rows up to 1.8 m high, three above that.
- Pickets: length ÷ (picket width + gap).
- Concrete: the volume of each post hole.
Worked example
A 40 m fence at 2.5 m spacing: 16 spans, 17 posts. Two rows of rails is 80 linear metres. A 100 mm picket with a 30 mm gap: 40,000 ÷ 130 = 308 pieces. With Ø25 cm holes 0.9 m deep: 17 × 0.044 = 0.75 m³ of concrete.
Embedment depth
A post must sit below the local frost line, otherwise frost heave pushes it out. Depth depends on the region and the soil. On heaving clay many builders replace solid concreting with compacted gravel backfill so water does not collect around the post.
Gates
Count gates separately: their posts are thicker (at least 80 × 80 mm for a 3.5–4 m opening), set deeper and often tied together below ground. Subtract the gate widths from the fence length if you do not want them counted as spans.
Construction Material Calculators
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