How This Calculation Works
The fence calculator subtracts gate openings from the total fence length, then divides the remaining length by the panel width to find how many panels you need. Posts are calculated as panels + 1 (one post between each panel, plus one at each end), with extra posts for gate openings.
Rails — the horizontal members that support panels — are estimated at 2 per panel for fences under 1.5 m (5 ft) and 3 per panel for taller fences, which need the extra rigidity.
Each post hole requires concrete for setting. The calculator estimates one bag per post, which is sufficient for most residential post holes (typically 25 cm / 10 in diameter, 60 cm / 2 ft deep).
Common Mistakes to Avoid
- Not checking property lines. Fences built even a few centimetres over the property line can result in costly disputes. Get a survey or confirm boundaries with your neighbor before you build.
- Ignoring slope. On sloped ground, you need to decide between stepping the fence (each panel at a different height) or racking it (tilting panels to follow the slope). Both approaches affect post spacing.
- Shallow post holes. Posts should be buried to at least one-third of the total fence height, plus an additional 15 cm (6 in) for gravel drainage. A 1.8 m fence needs holes about 75 cm (30 in) deep.
- Forgetting gate hardware. Hinges, latches, and gate frames are not included in the panel count. Budget for gate hardware separately and plan your gate width before ordering panels.
Worked Example
Scenario: A 30 m fence, 1.8 m high, with 1.8 m wide panels and 1 gate.
Step 1 — Gate allowance: 30 − 1 m (gate opening) = 29 m of fencing.
Step 2 — Panels: 29 ÷ 1.8 = 17 panels (rounded up from 16.1).
Step 3 — Posts: 17 + 1 + 1 (extra for gate) = 19 posts.
Step 4 — Rails: 17 × 3 (tall fence) = 51 rails.
Step 5 — Concrete: 19 bags (one per post hole).