How to Use the Fence Calculator
- Choose your units. USA mode uses feet and inches; UK mode uses metres and millimetres.
- Enter the total fence length, including gates. Measure along the line where the posts will go.
- Choose the layout. Pick "Open run" for a fence with two ends (such as a back boundary), or "Enclosed" for a fence that loops back to where it started.
- Enter the number of corners and gates, plus the gate widths. Each gate needs its own pair of posts.
- Choose the fence style and height. The calculator sets a typical post spacing, rail count and post depth, which you can change.
- Add prices (optional) to see the material or installed cost.
The result lists every component, with a small allowance for waste on pickets and boards.
How Many Fence Posts Do I Need?
The basic rule: posts = fence length ÷ post spacing, rounded up, plus one to close off the end. Corners, gates and ends all need posts of their own, so the calculator adds:
- One extra post for each corner, because a corner rarely lands exactly on your spacing.
- One extra post for each gate, so that the gate has a post on each side.
- No end post for an enclosed fence, because the run finishes on the post it started from.
Typical post spacing
| Fence type | Post spacing |
|---|---|
| Wood privacy or picket (USA) | 6–8 ft on center; 8 ft is standard, 6 ft in high-wind areas |
| Vinyl (USA) | Set by the panel width, usually 6 or 8 ft |
| Chain link (USA) | Up to 10 ft for line posts |
| Panel fencing (UK) | Panel width plus post: about 1.93 m centres for 1.83 m (6 ft) panels on 100mm posts |
| Closeboard / featheredge (UK) | 2.4–3.0 m, matching the arris or rail length |
Worked example (USA): wood privacy fence
A 150 ft, 6 ft tall wood privacy fence with one 4 ft gate and two corners, posts at 8 ft centres:
- Fence without the gate: 150 − 4 = 146 ft
- Sections: 146 ÷ 8 = 18.25, rounded up to 19
- Posts: 19 + 1 (end) + 2 (corners) + 1 (gate) = 23 posts, each 8 ft long (6 ft above ground, 2 ft buried)
- Rails: 3 per section for a 6 ft fence = 57 rails (2×4, 8 ft)
- Pickets: 5½-inch boards with a ¼-inch gap: 146 × 12 ÷ 5.75 = 305, plus 5% = 321 pickets
- Concrete: about 2 bags of 50 lb fast-setting mix per post = 48 bags
Worked example (UK): panel fence
A 20 m run of 1.8 m (6 ft) lap panels on concrete posts with gravel boards, and one 0.9 m gate:
- Fence without the gate: 20 − 0.9 = 19.1 m
- Panels at 1.93 m centres: 19.1 ÷ 1.93 = 9.9, rounded up to 10 panels and 10 gravel boards
- Posts: 10 + 1 + 1 (gate) = 12 posts. With a 150mm gravel board and 600mm in the ground, each post is about 2.55 m, so buy 2.7 m (9 ft) concrete posts.
- Postcrete: about 2 × 20 kg bags per post, so 24 bags
How Deep Should Fence Posts Be?
Two common rules give similar answers for a standard 6 ft (1.8 m) fence:
- One-third of the above-ground height: a 6 ft fence needs posts at least 2 ft (600mm) deep. This is the usual UK guidance and the calculator's default.
- One-third of the total post length: an 8 ft post buried 2⅔ ft; some US installers go to 3 ft for privacy fences in exposed areas.
In cold climates, set posts below the frost line, which can be 36–48 inches or more in the northern US. Otherwise frost heave can lift posts out of the ground over a few winters. Gate posts and corner posts take more load, so bury them deeper or use a bigger post (6×6 instead of 4×4, or 125mm instead of 100mm).
How Much Concrete Per Fence Post?
Dig the hole about three times the post's width: around 10–12 inches across for a 4×4 post (3½ inches actual), or 250–300mm for a 75–100mm UK post. Add about 4 inches (100mm) of gravel at the bottom for drainage.
The concrete needed is the hole volume minus the post. For a 4×4 in a 10-inch hole with 20 inches of concrete:
- Hole: 3.1416 × 5² × 20 = 1,571 cubic inches
- Post: 3.5 × 3.5 × 20 = 245 cubic inches
- Concrete: 1,326 cubic inches = 0.77 cubic feet, or about 2 bags of 50 lb fast-setting mix (each about 0.375 cubic feet), or 1.3 bags of 80 lb mix.
In the UK, a 100mm concrete post in a 250mm hole needs about 20 litres of postcrete. A 20 kg bag of postcrete makes roughly 10 litres, so plan on 2 bags per post. Always check the yield printed on the bag, because products differ.
If you're also pouring a slab or footing, the Concrete Calculator covers that.
Rails, Pickets, Panels and Boards
Rails (USA wood fences): use 2 rails for fences up to 4 ft tall and 3 rails for 5–6 ft privacy fences. Rails are usually 2×4s cut to the post spacing, so an 8 ft section uses one 8 ft board per rail.
Pickets: pickets = fence length (inches) ÷ (picket width + gap). Privacy fences use a gap of about ¼ inch or none; picket fences often leave a gap equal to about half the picket width. Board-on-board fences need roughly 1.5 times as many pickets because they overlap.
Panels (UK): standard panels are 1.83 m (6 ft) wide and come in heights from 0.9 m to 1.8 m. You need one panel per bay. Gravel boards sit under each panel to keep the timber off the soil, so order one per panel.
Closeboard and featheredge (UK): featheredge boards (usually 100–125mm wide) are fixed to 3 arris rails per bay for a 1.8 m fence, with each board overlapping the last by about 25mm. With 125mm boards and a 25mm overlap, you need 10 boards per metre.
Chain link (USA): order mesh to the full length, one top rail along the run, a tension wire at the bottom, and one tension bar per terminal post (two for each corner).
Fence Cost Estimates
USA (installed, per linear foot)
| Material | Typical installed cost |
|---|---|
| Chain link | $8–$40 |
| Wood picket | $5–$30 |
| Vinyl | $15–$40 |
| Composite | $11–$45 |
| Wrought iron | $25–$55 |
Many homeowners spend about $2,000–$5,000 on a typical fence, and professional installation commonly works out around $15–$25 per foot for standard wood.
UK
| Item | Typical cost |
|---|---|
| 6 ft lap panel (supply only) | £20–£50 each |
| Closeboard / featheredge panel (supply only) | £25–£60 each |
| Lap panel fence, installed | £70–£100 per metre |
| Closeboard fence, installed | £90–£130 per metre |
| Labour | about £40–£60 per panel, or £300–£400 per day |
Taking out an old fence adds cost, especially concrete-set posts (often £50–£100 per post). Costs rise with height, slope, poor access and rock in the ground.
Fence Height Rules and Permits
UK (England): under permitted development, you can usually put up a fence, wall or gate up to 2 metres high on side and rear boundaries without planning permission. Next to a highway used by vehicles, or the footpath beside it, the limit is 1 metre. Listed buildings and some conservation areas need permission whatever the height. Height is measured from the ground on your side, and trellis on top counts towards the total.
USA: rules are local. Many towns allow 6 ft in back yards and 3–4 ft in front yards, may require a permit, and set rules on which side faces out and how far back from the property line or sidewalk the fence must sit. HOAs often add their own rules on materials and colours. Check with your building department, and call 811 before you dig so buried utility lines can be marked.
Tips Before You Build
- Confirm the boundary. Check your property survey or title plan; if in doubt, set the fence slightly inside your line.
- Run a string line between end posts so the posts line up straight.
- Set end, corner and gate posts first, then fill in the line posts between them.
- Step or rack the fence on slopes. Panels are stepped; picket and chain link fences can follow the slope.
- Use treated timber rated for ground contact for posts (in the USA, look for "ground contact"; in the UK, Use Class 4).
- Talk to your neighbours first, especially on a shared boundary.
Frequently Asked Questions
How many fence posts do I need for 100 feet?
At 8 ft spacing with no gates or corners, 100 ÷ 8 = 12.5, so 13 sections and 14 posts. Add one post for each gate and corner.
How far apart should fence posts be?
8 ft is standard for wood fences in the USA, or 6 ft in windy areas. In the UK, panel fence posts sit about 1.93 m apart for 1.83 m panels on 100mm posts.
How deep should a fence post be for a 6 ft fence?
At least 2 ft (600mm), or a third of the height above ground. In cold climates, go below the frost line, often 3–4 ft.
How many bags of concrete per fence post?
About two 50 lb bags of fast-setting concrete for a 4×4 post in a 10-inch hole set 2 ft deep. In the UK, about two 20 kg bags of postcrete per post.
How many pickets do I need for an 8 ft section?
With 5½-inch pickets and a ¼-inch gap, about 17 pickets per 8 ft section (96 ÷ 5.75 = 16.7).
How many fence panels do I need?
Divide the fence length (minus gates) by the post centres, usually 1.93 m for 1.83 m panels on 100mm posts, and round up. A 20 m fence with a 0.9 m gate needs 10 panels.
What height of fence can I put up without planning permission in the UK?
Up to 2 m on side and rear boundaries, and up to 1 m next to a road used by vehicles or its footpath.
What length of post do I need for a 6 ft fence?
In the USA, an 8 ft post (6 ft above ground, 2 ft below). In the UK, a 2.4 m post without a gravel board, or 2.7 m with a 150mm gravel board.
Get quotes from local fencing contractors
A fencer can check your boundary, ground conditions and local rules. Compare at least three quotes.