What this planner works out
This planner divides a fence run by the panel width to give the number of panels, then works out the posts, gravel boards and approximate postcrete needed, adjusting for a gate if you include one.
The post count is the one people get wrong. A run of panels needs one more post than panels, and a gate needs a post on each side.
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Before you order
- Measure the actual run, and check whether the boundary is where the existing fence stands. Deeds settle it, not habit.
- Standard UK fence panels are 1.83 m wide. Add the post width when setting out — posts are typically 75 or 100 mm.
- Gravel boards raise the panel clear of the ground and are the single best thing you can do for panel life.
- Two bags of postcrete per post is a reasonable estimate for a standard hole; deep or wide holes need more.
A timber panel in contact with soil wicks moisture and rots from the bottom within a few years. A concrete or timber gravel board takes that contact instead and can be replaced on its own for a fraction of the cost of a panel. Fitting them roughly doubles the working life of a fence.
How this calculator works
Panels, then posts:
Panels = fence length ÷ panel width, rounded up, less one if a gate is included
Posts = panels + 1, plus two more if a gate is included
Postcrete ≈ 2 bags per post · Gravel boards = one per panelThe gate adjustment removes one panel and adds two posts, on the basis that a gate replaces a panel and needs a dedicated post each side. Real gates vary in width, so check yours against the panel it replaces.
Worked example: a 12 m run
Using the default figures — 12 m of fence in 1.83 m panels with no gate:
- Panels: 12 ÷ 1.83 = 6.56, rounded up to 7
- Posts: 8
- Postcrete: about 16 bags
- Gravel boards: 7
Seven panels at 1.83 m is 12.81 m of fence for a 12 m run, so the last panel needs cutting down — or the run needs setting out to finish on a post. Panel fencing does not adjust, so deciding in advance where the odd measurement goes, usually at the least visible end, is part of setting out rather than something to discover at the last post.
Common mistakes
- Ordering as many posts as panels. A run needs one more.
- Forgetting the post width when setting out. Eight posts at 100 mm adds 800 mm to the run.
- Skipping gravel boards. They roughly double panel life.
- Assuming the boundary line. Check the deeds before moving a fence.
- Concreting posts before checking the run is straight. Set a string line first.
Frequently asked questions
Concrete or timber posts?
Concrete posts outlast timber and are the usual choice with gravel boards, since the panel slots straight in and can be replaced without disturbing the post. Timber posts look better and are easier to fix things to, but rot at ground level eventually however well treated. Many people use concrete posts with timber panels as a compromise.
Do I need permission to replace a fence?
Replacing a fence like for like generally does not need planning permission, provided height limits are respected — typically 2 m, or 1 m adjoining a highway used by vehicles. Listed buildings, conservation areas and specific planning conditions may differ. Ownership is a separate question and is set out in the deeds.
How do I handle a sloping site?
Two approaches: stepping, where each panel stays horizontal and the fence steps down at each post, or raking, where panels follow the slope. Stepping is far easier with standard panels and leaves triangular gaps at the bottom that gravel boards can partly close. Raking generally needs close-boarded construction built on site.
What is the difference between panel types?
Waney lap is cheapest and shortest-lived. Featheredge or close-boarded is built from individual boards, is far more durable and can follow a slope. Overlap and tongue-and-groove panels sit between the two. Cost broadly tracks the amount of timber and how well it sheds water.
Is what I enter stored?
No. Measurements are processed in your browser and never transmitted or retained.
Related tools
References
- GOV.UK — planning rules on fences and boundaries, and Land Registry title information
- Health and Safety Executive — avoiding underground services and safe manual handling
Sources are checked at publication and can change — how I choose and check references.