Fence Calculator — Posts, Rails, Pickets & Concrete
Calculate fence posts, rails, pickets or panels, concrete footing volume and post caps for any fence length, height and style. Supports wooden picket, close-board, post-and-rail, palisade and panel fencing.
How many fence posts do I need?
Divide the fence length by the post spacing and add one for the end post, then round up. Spacing is usually set by the panel or rail length — commonly 1.8–3.0 m, or 6–10 ft. A 24 m run at 1.8 m centres is 13 spans, so 14 posts.
How much concrete does one fence post take?
It is the hole volume: π × (diameter ÷ 2)² × depth. A 200 mm wide, 600 mm deep hole is 0.019 m³ — about 1½ bags of 25 kg premix. In US sizes an 8 in by 24 in hole is roughly 0.67 cu ft, near enough one 80 lb bag. Bury about a third of the post’s total length as a starting point.
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How the fence calculator works
- 1Post count: fence length ÷ post spacing + 1 (for end post), round up
- 2Rail length: fence length × number of rail rows (or spans × span length × rail rows)
- 3Picket count: fence length ÷ (picket width + gap) × number of picket rows
- 4Concrete per post: π × (hole diameter/2)² × hole depth (typically 1/3 of post above ground)
- 5Total concrete: concrete per post × post count
- 6Add 10% waste for rails and pickets; posts are bought per item
Worked example
Fence: 30 m long, 1.8 m high — 100 × 6 ft — posts at 2.4 m (8 ft) spacing, 3 rails, 75 mm pickets with 25 mm gaps: 3 in pickets, 1 in gaps.
Posts: 14 (13 spans + 1 end post). Rails: 39 × 2.4 m = 93.6 lm, or 307 linear feet. Pickets: 300. Concrete: 14 × 0.019 m³ = 0.27 m³ — 9.5 cu ft — in 23 bags of 25 kg premix, using 200 mm dia × 600 mm holes (8 in across, 24 in deep).
Frequently asked questions
How many fence posts do I need for 30 metres of fence?
At 2.4 m spacing — 8 ft — 30 ÷ 2.4 + 1 = 13.5 → 14 posts (always round up and add one for the end post). At 1.8 m (6 ft) spacing: 18 posts.
How deep should fence posts be set?
The rule of thumb is 1/3 of the total post length below ground. For a 1.8 m fence with 2.4 m posts: 600 mm (24 in) deep in concrete. In loose or wet soils, go deeper — 750 mm, or 30 in, minimum.
How much concrete do I need per fence post?
A standard 200 mm diameter hole at 600 mm deep — 8 in across, 24 in down — uses approximately 0.019 m³ (0.67 cu ft) of concrete, just under one 25 kg bag. Allow one bag per post for convenience; pour dry-mix and add water for small quantities.
What post spacing should I use for a fence?
1.8 m — 6 ft — is the most common for close-board and panel fencing (panels are typically 1.8 m wide). 2.4 m, or 8 ft, works for post-and-rail and lighter picket fencing. Do not exceed 2.4 m for tall fences.
How long does a timber fence last?
Pressure-treated softwood (rated for ground contact): 15–25 years. Hardwood (oak, sweet chestnut): 25–40 years. The key is proper post protection — use metal post spikes or set posts in free-draining concrete.
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