How the Fence Panel Calculator Works

Enter your total fence run, panel height, post width, and gravel board choices. The calculator divides the run by the standard panel width, rounds up to whole panels, adds one more post than panels, and totals the gravel boards and postcrete to match.

The core numbers are straightforward: UK fence panels are 1.83m (6ft) wide as standard, and posts always number panels plus one. A 15-metre run works out at 15 ÷ 1.83 = 8.2, which means 9 panels and 10 posts. For precise runs, it is worth knowing the posts themselves take up ground: a 100mm concrete post between each panel stretches 9 panels to roughly 17.5 metres of actual fence line, which is why measuring and marking post centres beats dividing on paper alone.

Getting the Post Length Right

The mistake that ruins more fence orders than any other is buying posts the same length as the fence is tall. Posts need 600mm in the ground as a minimum, rising to 750mm on exposed or windy sites, so a 1.8m (6ft) fence needs 2.4m (8ft) posts. If you add gravel boards, remember they raise the fence by 150mm, so a 1.8m panel on a gravel board needs a post that carries 1.95m above ground.

On post material, the trade has largely settled the argument: slotted concrete posts cost more upfront but last 20 years plus and let panels slide out for replacement, while 100 × 100mm timber posts look warmer but typically fail at ground level in 10 to 15 years. One compatibility note merchants will not always volunteer: concrete gravel boards need concrete slotted posts, since timber posts have nothing to hold them.

Gravel Boards Earn Their Money

A £10 to £20 gravel board protects a £40 to £70 panel: that is the whole argument in one sentence. Sitting between the ground and the panel, the gravel board takes the soil contact, splash, rot, and can be swapped cheaply when it eventually decays. Fences without them rot from the bottom edge years earlier.

Concrete boards in 150mm or 300mm heights suit slotted post systems, with taller boards solving the common problem of soil sitting higher on one side of a boundary. A small kindness worth copying: hedgehog-friendly gravel boards with a ground-level gap keep garden wildlife corridors open. Postcrete completes the order at 1 to 2 bags per post in firm ground, and 2 to 3 bags in soft ground or for taller fences.

Panels, Prices and Lifespan

Panel choice sets both the budget and the lifespan. Waney lap panels are the budget option at roughly £25 to £40 each, fine in sheltered gardens but good for only 8 to 15 years. Closeboard style panels, with vertical featheredge boards on a framed panel, cost £45 to £70 and last 15 to 20 years with treatment, handling wind far better.

Supply and fit prices currently run about £60 to £90 per metre for lap and £80 to £120 for closeboard, with fencer day rates at £200 to £300, so a DIY install typically saves 30% to 40%. On sloping gardens, panels must step down in fixed increments, leaving triangular gaps at the bottom that gravel boards partially solve. Where the slope is serious, fencing built board-by-board follows the ground far better, and our dedicated Closeboard Fencing Calculator UK covers that system in full.

Worked Example and the Legal Bits

A 20-metre rear boundary in 1.8m closeboard panels on concrete posts with gravel boards:

• Panels: 20 ÷ 1.83 = 10.9, so 11 panels.
• Posts: 12 slotted concrete at 2.7m to carry the panel plus gravel board.
• Gravel boards: 11 concrete at 150mm.
• Postcrete: 24 bags for firm ground.
• Order: Order a spare panel from the same batch for future repairs.

On rules, fences up to 2 metres need no planning permission in most gardens, dropping to 1 metre beside a highway, with conservation areas and some new-build estates carrying extra restrictions. Boundary ownership comes from your title deeds, where a T-mark points at the owner, and a new fence should sit just inside your own boundary unless a neighbour has agreed otherwise.