How to Use the Fence Panel Calculator
- Enter the length of the fence in metres (or feet). Measure along the line where the posts will go.
- Add any gates and their widths. Each gate opening is taken out of the panel run and gets its own posts.
- Choose the panel height: 0.9m (3ft), 1.2m (4ft), 1.5m (5ft) or 1.8m (6ft).
- Choose the post type: 75mm or 100mm timber, or 100mm concrete slotted posts.
- Tick gravel boards if you're using them (recommended).
- Tell the calculator about corners and whether the fence is an enclosed loop.
- Add prices for panels, posts and gravel boards (optional) to see the material cost.
How Many Fence Panels Do I Need?
Standard UK fence panels are 1.83m (6ft) wide. Because each post takes up space too, panels are spaced at panel width + post width:
| Post type | Post width | Post centres |
|---|---|---|
| 75mm timber | 75mm | about 1.905m |
| 100mm timber | 100mm | about 1.93m |
| 100mm concrete slotted | 100mm | about 1.93m |
Panels = fence length (minus gates) ÷ post centres, rounded up. The last bay is often shorter than a full panel, so you'll either cut a panel down or use a narrower one.
Posts = panels + 1 for a straight run, plus 1 per gate and 1 per corner. An enclosed fence that returns to its start needs one fewer.
Worked example: 15m garden fence
A 15m straight fence with 1.8m lap panels on 75mm timber posts, with no gates:
- Panels: 15 ÷ 1.905 = 7.9, rounded up to 8 panels
- Posts: 8 + 1 = 9 posts
- Post length: 1.8m panel + 600mm in the ground = 2.4m, so buy 2.4m posts. With a 150mm gravel board under each panel, you'd need 2.55m, so buy 2.7m posts.
- Fence clips: 3 per side of each panel = 48 clips
- Postcrete: about 2–3 bags of 20kg per post, so about 20 bags
- Gravel boards: 8
Worked example: concrete posts with a gate
A 20m fence with 1.8m panels, 100mm concrete posts, gravel boards, and one 0.9m gate:
- Fence without the gate: 19.1m ÷ 1.93m = 9.9, so 10 panels and 10 gravel boards
- Posts: 10 + 1 + 1 (gate) = 12 posts, each 2.74m (9ft) for a 6ft panel on a gravel board
- Postcrete: about 24 bags
Panel Sizes and Types
Common sizes (width × height): 6ft × 6ft (1.83 × 1.83m), 6ft × 5ft (1.83 × 1.52m), 6ft × 4ft (1.83 × 1.22m) and 6ft × 3ft (1.83 × 0.91m). Some ranges also come in 1.8m and 0.9m widths, so check before you work out post spacing.
Common types
- Lap (overlap) panels: the cheapest. Thin horizontal boards overlap. Fine for sheltered gardens, but less sturdy in strong wind.
- Closeboard panels: vertical featheredge boards on a strong frame. Stronger, more private and longer-lasting.
- Hit and miss: boards alternate on each side, letting wind through while looking good from both sides. Good for exposed sites.
- Slatted and contemporary panels: horizontal slats with small gaps, popular for modern gardens.
- Trellis panels: used on top of a fence for climbers, or as a screen.
In windy areas, choose panels that let some air through, and use 100mm posts or concrete posts. Solid lap panels act like a sail.
If you're building a fence with featheredge boards fixed on site, or need a fence in feet for the USA, use our Fence Calculator, which covers those styles.
Timber Posts or Concrete Posts?
Timber posts (75 × 75mm or 100 × 100mm, pressure-treated) are cheaper and easier to cut, and panels are fixed to them with clips or brackets. Use 100mm posts for 6ft fences in exposed spots. Look for posts treated for ground contact (Use Class 4).
Concrete slotted posts have a channel on each side that the panel drops into. They don't rot, last decades, and let you replace a blown-down panel without disturbing the post. They're heavier to handle and cost more. Use them with concrete gravel boards that slot into the same channel.
Post lengths to buy
| Panel height | Timber post (no gravel board) | Concrete post (with 150mm gravel board) |
|---|---|---|
| 0.9m (3ft) | 1.5m | 1.75m |
| 1.2m (4ft) | 1.8m | 2.1m |
| 1.5m (5ft) | 2.1m | 2.36m |
| 1.8m (6ft) | 2.4m | 2.74m |
The rule is roughly a quarter to a third of the post below ground, with at least 600mm for a 6ft fence. Corner and gate posts take more strain, so set them deeper or use a heavier post.
How Much Postcrete Per Post?
Postcrete (rapid-setting post mix) comes in 20kg bags that make roughly 10 litres of concrete each. Check your bag, as yields vary.
For a hole about 250mm across and 600mm deep, with about 100mm of gravel at the bottom:
- 75mm timber post: about 22 litres of concrete, so roughly 2–3 bags
- 100mm post: about 20 litres, so roughly 2 bags
The calculator works this out from your hole size and post size. Pour water into the hole first, add the postcrete, and keep the post plumb while it sets (usually 5–10 minutes).
Fence Panel Prices and Installation Costs
| Item | Typical cost |
|---|---|
| 6ft lap panel (supply only) | £20–£50 |
| 6ft closeboard panel (supply only) | £25–£60 |
| Lap panel fence, supplied and fitted | £70–£100 per metre |
| Closeboard fence, supplied and fitted | £90–£130 per metre |
| Fitting labour | £40–£60 per panel, or £300–£400 a day (about 10–15 panels) |
| Removing old posts set in concrete | £50–£100 per post |
For a 15m lap panel fence, that's roughly £1,050–£1,500 fitted. Fencing on slopes, poor access, rocky ground or removal of an old fence all push the price up.
Fencing on a Slope
Panels must stay level, so on sloping ground you step them: each panel sits a little lower than the last, and the gap underneath is filled with a gravel board (or two stacked). Measure the horizontal length of the run, not along the ground. You'll need longer posts on the downhill side of each step, so allow the step height on top of the normal post length.
Fence Height Rules
In England, you can usually put up a fence up to 2m high on side and rear boundaries without planning permission, and up to 1m next to a road used by vehicles (or the footpath beside it). A 1.8m panel on a 150mm gravel board comes to 1.95m, just under the limit; adding trellis on top usually takes you over it. Listed buildings, conservation areas and some new estates have stricter rules, so check with your council first.
Replacing Panels Only
If your posts are sound and only the panels have blown out or rotted, you just need replacement panels (and clips or new gravel boards if needed). Measure the gap between posts before buying: older fences may have been built with slightly different spacing. With concrete posts, lift the old panel out of the slots and drop the new one in.
Frequently Asked Questions
How many fence panels do I need for 20 metres?
About 11 panels with 100mm posts (20 ÷ 1.93 = 10.4, rounded up), or 10 if a 0.9m gate takes up part of the run.
How many posts do I need for 10 fence panels?
11 posts for a straight run, plus one extra for each gate and corner.
How far apart are fence posts for 6ft panels?
About 1.905m centre to centre with 75mm posts, and 1.93m with 100mm posts.
How deep should fence posts be?
At least 600mm for a 6ft (1.8m) fence, or about a quarter to a third of the post's length.
How many bags of postcrete per post?
Usually 2 bags of 20kg for a 100mm post in a 250mm hole, and 2–3 bags for a 75mm post.
What length post do I need for a 6ft fence?
2.4m for timber posts without gravel boards, or 2.74m concrete posts with a 150mm gravel board.
Do I need gravel boards under fence panels?
They're strongly recommended. A gravel board keeps the bottom of the panel off the soil so it doesn't rot, and it's much cheaper to replace a gravel board than a whole panel. Concrete gravel boards last longest and suit concrete posts; timber boards fit timber posts.
Can I put up fence panels myself?
Yes, panel fencing is a common DIY job, but it's easier with two people. Set the end posts first, run a string line between them, and fix each panel before setting the next post so the spacing stays right.
Do I need planning permission for a 6ft fence?
Usually not on side and rear boundaries, as long as the total height stays under 2m. Next to a road, the limit is 1m.
Get quotes from local fencing contractors
A fencer can check your boundary, ground conditions and local rules.