Fence Calculator (Posts & Panels)
By Santaji GadepatilinUpdated October 27, 2026
The number of fence posts and panels depends on the fence length and post spacing. Planning it correctly avoids extra trips to the supplier.
How to use the fence calculator
Enter the fence length, post spacing and rails per section. The number of panels, posts and rails is calculated. Add extra posts for corners and gates.
Example
30 m of fence with 1.83 m panels and 3 rails per section:
- Panels = 17
- Posts = 18
- Rails = 51
Posts and panels for common lengths
1.8 m (6 ft) panels:
| Fence length | Panels | Posts | Rails (3 per section) |
|---|---|---|---|
| 10 m | 6 | 7 | 18 |
| 20 m | 12 | 13 | 36 |
| 30 m | 17 | 18 | 51 |
| 50 m | 28 | 29 | 84 |
| 100 m | 56 | 57 | 168 |
Add one extra post for each corner and gate, and two posts for each gate opening.
Post depth
A common rule is to bury one-third of the post’s total length, or at least 600 mm. For a 1.8 m fence, use 2.4 m posts set about 600 mm deep. Use deeper holes in soft ground or exposed, windy sites.
Concrete per post
A 300 mm diameter hole 600 mm deep, minus a 100 × 100 mm post, needs about 0.036 m³ — roughly four 20 kg bags of post-mix (each makes about 0.01 m³). See the concrete column calculator.
Picket fences
For a picket fence, also count pickets:
Pickets = fence length ÷ (picket width + gap)
30 m of 90 mm pickets with 50 mm gaps needs about 30,000 ÷ 140 = 215 pickets.
Before you build
- Check boundary lines and local height limits.
- Locate underground services before digging.
- Ask neighbours if the fence is on a shared boundary.
Concrete for posts
A post hole of 300 mm diameter and 600 mm deep takes about 0.04 m³ of concrete. Use the column calculator for exact amounts.
Frequently asked questions
How many fence posts do I need?
Divide the fence length by the post spacing, round up, and add one for the end post.
What spacing should posts have?
Standard panels are about 1.83 m (6 ft) wide; post-and-rail fences often use 2–2.4 m (8 ft).
How deep should posts go?
A common rule is about a quarter to a third of the post's above-ground height, typically 600 mm for a 1.8 m fence.
How many posts do I need for a 30 m fence?
With 1.8 m panels, 17 panels and 18 posts, plus extras for corners and gates.
How far apart should fence posts be?
Usually 1.8–2.4 m (6–8 ft), depending on panel size and wind exposure.