Fence Calculator
Calculate fence panels, posts, concrete and materials for your garden fence. Choose height, panel width, and add gates. Get a full shopping list with cost estimates.
Fence Length
Fence Specifications
Post Fixing
1× 20kg bag per post depth
Optional Additions
Gravel Board
One board per panel (prevents rot at base)
Include Gate
Pricing
Results
Fence Length
20.00 m
Fence Height
1.8m
Materials Needed
Cost Breakdown
Total Cost
£431.00
Panels, Posts and the Bag of Concrete You Forget
Standard UK lap-panel fencing is sold in 1.83 m (6 ft) wide panels at heights from 0.9 m to 1.8 m. A 20 m run of 1.8 m panels (the default here) needs 11 panels and 12 posts, because there is always one more post than panel. At roughly £25 a panel and £8 a post that is £371 in timber alone before fixings. Add a 20 kg bag of postcrete per post (£3 each) and post caps at £2 a piece, and the total drifts past £450 just for the basics.
Concrete-set posts last 15 to 20 years if the timber is pressure-treated and the concrete is dome-shaped to drain water away from the post base. Metal post spikes are quicker to install (no waiting for the concrete to set) but only suit short panels in firm ground; on a windy site, anything above 1.5 m wants concrete. Swap the fixing type in the calculator and the materials list adjusts.
Adding a Gate Changes the Posts
A single gate is typically 0.9 m wide and a double gate around 3 m. The calculator subtracts the gate from the panel length so the run still works out, but a gate post is doing more work than a panel post and usually steps up to a heavier 100 mm by 100 mm timber or a metal gate post with concrete in. Budget around £35 for a single gate, £45 for a double, plus the heavier gate post.
Gravel boards underneath the panel keep the panel itself off wet ground and add a second life to the timber. They cost around £3 each and are worth every penny on a fence that runs along a flower bed. For the patio and driveway groundwork that sometimes ties in with a new fence, [Gravel Calculator](/gravel-calculator) handles the aggregate side.
Frequently Asked Questions
How many fence panels do I need for 20 metres?
Eleven 1.83 m panels covers 20.13 m, just over the run. You also need 12 posts (panels plus one), 12 post caps and 12 bags of postcrete if setting in concrete. Add gravel boards if you want the panels held off the ground.
How deep should fence posts be?
For a 1.8 m fence, sink the post at least 600 mm into the ground (so use a 2.4 m post). Heavier or windier sites benefit from 750 mm. The hole should be roughly three times the post width across, filled with concrete that domes upwards above ground level to shed water.
Concrete or metal post spikes?
Concrete is the standard for fences over 1.5 m or in soft ground; spikes shake loose under wind load on tall panels. Spikes work fine for 0.9 m garden borders or for replacing a single failed post in firm clay. Most installers use concrete by default.
Whose fence is it on the boundary?
Check the deeds. There is no legal default in England and Wales; a T mark on the plan points to the side responsible for that boundary. If the deeds are silent, neighbours often agree informally to share the cost. Always have the conversation before driving a post in.
Related Tools
Gravel Calculator
Calculate how much gravel, aggregate or sand you need in tonnes and bags. Enter your area and depth, select material type, and get accurate quantities with cost estimates.
Concrete Calculator
Calculate concrete volume, cement bags and mix ratios for slabs, circular pads and post holes. Get quantities for premix bags or DIY mixing with cost estimates.