Fencing Calculator — Panels & Cost

Fence panels in the UK are a standard 1.83 m (6 ft) wide. The number of panels is calculated by dividing the total run length by 1.83 m and rounding up, so a 12m run gives 6.6, which means 7 panels. You need one more post than the number of panels, because posts go at each end and between every panel, so those 7 panels need 8 posts. Standard fence post height is the panel height plus 600 mm for the buried portion (or 450 mm if using post supports). In exposed or windy locations, sink the posts 750mm into the ground instead.

This calculator estimates panels, posts, post-fix concrete (1–2 bags per post), gravel boards (optional, placed at ground level to protect panels from damp) and post caps. For closeboard fencing (individual boards on rails), it calculates featherboard quantity, arris rails and clips instead. Enter the total fence run length, panel height (typically 0.9 m, 1.2 m, 1.5 m or 1.8 m) and fence type, and it shows the materials and an estimated cost. Planning permission is not normally needed for fences up to 2 m high (1 m if adjacent to a highway). Trellis on top counts towards the height, and trees and hedges over 2m can fall under the High Hedges Act if they block a neighbour's light.

Panel type drives both cost and lifespan. Lap panels (waney edge, overlap) are the budget choice at £25-£50 each and last 7-10 years. Featheredge or closeboard panels with vertical boards cost £50-£100, are sturdier and last 10-15 years. Hit-and-miss panels with boards alternating on each side cost £55-£90 and let wind through, which suits exposed sites. Tongue and groove at £70-£130 is the high-end residential option. Concrete gravel boards at £30-£60 each give a rot-proof bottom row, and a 300mm trellis topper adds £15-£40 per panel. Concrete posts cost £20-£35 each, while pressure-treated 4x4 timber posts (100×100mm) are £15-£25.

Posts and their footings decide how long the fence stands. A 1.8m fence needs posts at least 600mm into the ground. Postcrete comes in 20kg bags at £5-£8, sets in 5-10 minutes, and you need 1-2 bags per post, so each hole costs £10-£15 in concrete. Standard concrete is cheaper but takes 24 hours to set, which is why rapid-set postcrete is the usual choice for fencing. Fitting concrete spurs at the base of timber posts keeps the timber out of ground contact and extends its life by 5-10 years.

Before replacing a boundary fence, check who owns it. Ownership is shown on the Title Deed, which costs £3 to download from the Land Registry, and by convention a 'T' mark on the deed plan points to the owner. Many UK properties have shared boundaries where neither neighbour solely owns the fence. You may paint or repair your own side without permission, but you cannot paint, attach anything to or alter the neighbour's side. The height limit without planning permission is 2m, dropping to 1m next to a highway, which is why front gardens beside a road are usually fenced at 1m (3ft 3in) while rear and side gardens run to 1.83m (6ft).

Costed as a DIY job, a 12m fence of 7 panels and 8 posts comes to about £640 in materials: panels £300, posts £200, postcrete £40 and gravel boards £100. Tools such as a post-hole digger, spirit level and string line add £40-£100, and two people should allow 2 days. A professional installer charges £20-£40 per metre fitted depending on complexity, so £240-£480 in labour for 12m and a total of £900-£1,400. Gates cost £150-£400 each plus £80-£150 to fit. Annual staining or treatment costs £20-£40 in product and about 4 hours of work, and extends panel life by 50-100%.