Fence Post Calculator
Enter the total fence length, post spacing and hole size to calculate the number of posts and the foundation concrete volume.
Input Data
Results
At a glance:Fence posts are placed along the total length at a fixed centre spacing; count = ⌊total length ÷ spacing⌋ + 1 (including both ends). Each post sits in a circular concrete footing whose volume = π r² × depth (r = hole radius, depth = embedment); total = per-hole volume × post count × (1 + waste). Embedment must resist uplift and overturning, so increase depth in high wind or soft soil. This calculator covers posts and footing concrete only, excluding rails, mesh and backfill.
Formula
Post count = ⌊total length / spacing⌋ + 1
Per hole = π × (hole diameter / 2)² × depth
Total concrete = per hole × post count × (1 + waste%)
$$n = \left\lfloor \frac{L}{s} \right\rfloor + 1$$$$v = \pi r^2 d$$$$V = v \cdot n (1+w)$$How to Use
- Enter the total fence length (m).
- Enter the post spacing (commonly 2.4 m).
- Enter the hole diameter and depth (mm).
- The tool outputs the post count and total concrete.
Case Studies
Garden fence of a residential flat
24 m, spacing 2.4 m, hole dia 300, depth 600, waste 5%.
11 posts; 0.0424 m³ per hole; total concrete about 0.489 m³.
Front yard fence of a village house
36 m, spacing 3 m, hole dia 400, depth 800, waste 5%.
13 posts; 0.1005 m³ per hole; total concrete about 1.37 m³.
FAQ
Why does embedment depth matter?
Post embedment resists wind uplift and overturning. Hong Kong has many typhoons, so in soft soil or for tall fences increase depth to 600–900 mm or more.
Does spacing affect cost?
Wider spacing means fewer posts and less concrete but longer spans, which must match the rail and mesh strength. 1.8–3 m is common.
Related Tools
References
Content review: Calculatorism Editorial Team. Results are for reference only; please refer to the relevant authorities for the official figures.