Fence Calculator
Fence calculator — enter the total run length and your panel width to get the number of fence panels, posts and rails you need. Works for timber, composite and metal panel fencing. Runs in your browser.
Fence Calculator
How to Use the Fence Calculator
Measure the run
Enter the total fence length in metres.
Set panel width
Use your panel’s width (1.83 m is common).
Choose rails
2 for low fences, 3 for tall ones.
Read the materials
See posts, panels and rails to order.
Getting the Post Count Right
The single most common fencing mistake is buying the wrong number of posts — and it is almost always one short. The reason is a small but crucial counting quirk: a straight fence needs one more post than it has panels. Three panels need four posts, ten panels need eleven, because every internal post is shared between the two panels on either side of it, while the two ends each need their own. This calculator takes your total run length and panel width, works out how many panels (sections) fit, and then adds the extra end post automatically, so you never make that off-by-one error at the merchant’s counter.
Beyond posts and panels, it estimates the horizontal rails. Lower fences, up to around 1.2 metres, are typically built with two rails per section, while taller fences of 1.8 metres and above use three for rigidity — closeboard fences especially benefit from the extra rail. Enter the rails-per-section that suits your height and the tool multiplies it across all the sections. The default panel width is 1.83 metres (six feet), the standard size for UK timber and composite panels, but you should always enter the actual dimensions of the panels you intend to buy, since systems vary and individual-board fences are spaced by post centres instead.
A few realities live outside the material count but matter for the job. Posts are set in concrete for stability, with roughly a quarter to a third of their length buried — a 2.4 metre post suits a 1.8 metre fence — and taller or wind-exposed fences need deeper, wider footings. Gravel boards at the base of each panel take the damp from the ground and extend the life of the more expensive panels, so add one per section to your list if you use them. It is also worth checking the rules before you start: many areas cap fence height at about two metres without planning permission, and you should know which boundary is actually yours. For an L-shaped boundary, calculate each straight run separately and subtract the shared corner posts so you do not double-count. Buy a spare post and panel to cover damage or ground surprises, and as with every RECATOOLS tool, the calculation runs entirely in your browser, so your measurements stay private.
A straight fence always needs one more post than panels — the off-by-one that sends people back to the merchant mid-build.
10 Facts About Fencing
A fence always needs one more post than panels.
UK panels are commonly 1.83 m (6 ft) wide.
Posts are set in concrete for stability.
Set posts roughly a third of their length in the ground.
Taller fences usually need three rails, not two.
Gravel boards protect panels from ground moisture.
Check boundary ownership before you build.
Many areas cap fence height at 2 m without permission.
Concrete posts outlast timber ones.
This calculator runs in your browser — nothing is uploaded.
Frequently Asked Questions
- Divide your total run length by the panel width and round up to get the number of panels (sections), then add one — a fence always needs one more post than the number of panels, because each panel sits between two posts and the posts are shared. This calculator does that automatically and also estimates the rails.
- Picture three panels in a row: there is a post at the start, a post between the first and second panel, a post between the second and third, and a post at the end — four posts for three panels. Every internal post is shared by two panels, so the count is always panels plus one for a straight run.
- Use the actual width of the panels you are buying. In the UK, timber and composite fence panels are very commonly 1.83 metres (6 feet) wide, which is the default. Other systems differ, so check the product dimensions. If you are using individual boards rather than ready-made panels, enter the spacing of your post centres instead.
- Most fences up to about 1.2 metres use two horizontal rails (arris rails) per section; taller fences, typically 1.8 metres and above, use three for rigidity. The calculator multiplies your chosen rails-per-section by the number of sections. Closeboard fences in particular benefit from three rails.
- A common rule of thumb is to bury about a third to a quarter of the post’s total length, set in concrete, for a typical garden fence — so a 2.4 metre post for a 1.8 metre fence leaves 0.6 metres in the ground. Taller or exposed fences need deeper, wider footings. Always check local guidance for windy or boundary sites.
- They are optional but recommended. A gravel board sits at the base of each panel, taking the contact with damp ground so the more expensive panel stays dry and lasts longer. If you use them, you need one per section, matching the panel width. This calculator focuses on posts, panels and rails; add gravel boards to your list separately.
- In many countries, fences over about 2 metres (and sometimes 1 metre next to a road) require planning permission, and rules differ by location. Boundary ownership also matters — you should know which boundary is yours before building. Check your local authority’s rules; this tool only estimates materials, not regulations.
- It assumes a single straight run. For an L-shaped or multi-sided boundary, calculate each straight section separately and remember that a corner post is shared between two runs, so add the sections and subtract the shared corner posts to avoid double-counting.
- A small surplus is wise. Posts and panels can be damaged in transit or installation, and ground conditions sometimes force an extra post. Buying one spare post and panel, especially if matching a specific colour or style, avoids a delay and a possible mismatch later.
- Completely free, with no account or limit. It works offline once the page has loaded and collects no data.
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