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Fence Post Spacing Calculator — Posts, Panels & Postcrete
Calculate fence post quantities, panel numbers and postcrete bags for your fence run. Based on standard UK panel sizes.
Total length of the fence run, in metres
Protects fence panels from ground moisture
Adds 5% extra postcrete
5% recommended for postcrete
Enter your supplier price for a cost estimate
Enter your supplier price for a cost estimate
20kg bags of Postcrete (Post Mix) per post. Default 2 is conservative — a 100mm post in a 200×600mm hole needs ~1 bag; allow 2 for wider 300mm holes or exposed/gate posts.
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How We Calculate This
Our fence post calculator works by dividing your total fence run length by the panel width to determine the number of panels, then adds one extra for the end post.
The formula
Number of panels = Total length ÷ Panel width (rounded up)
Number of posts = Panels + 1
Postcrete bags = Posts × bags-per-post (default 2)
The default of 2 × 20kg bags per post is a conservative planning figure. A 20kg bag of Postcrete yields roughly 0.01 m³ (10 litres), so a 100mm post in a standard 200 × 600mm hole needs about 1 bag; allow 2 for wider 300mm holes, gate posts or exposed sites. Adjust the bags-per-post figure in advanced options to suit your hole size.
UK standard sizes
- Standard panel width: 1.83m (6ft) — most common UK size
- Post size: 75mm × 75mm or 100mm × 100mm
- Post length: 2.4m (8ft) for 6ft panels (600mm in ground)
- Postcrete: 1-2 × 20kg bags per post
- Gravel boards: 1.83m × 150mm per panel bay
Note: If your fence run is not an exact multiple of the panel width, you may need to cut the last panel to fit. The calculator rounds up to whole panels. For corners and direction changes, add an extra post at each corner.
Frequently Asked Questions
In the UK, standard fence panels are 1.83m (6ft) wide, so posts should be spaced exactly 1.83m apart (centre to centre of each post slot). For post-and-rail fencing, posts are typically spaced 2.4m-3m apart. Never exceed 3m between posts as the fence will be weak in strong winds. This fence post spacing calculator handles standard UK panel sizes and custom widths.
For a standard 75mm or 100mm fence post set 600mm deep, you need 1-2 bags of postcrete (20kg each). For 4-inch (100mm) posts in exposed locations, use 2 bags per post. A 20kg bag of postcrete (also called post mix or quick-set concrete) sets a post in about 5-10 minutes — just add water directly into the hole.
Fence posts should be buried at least 600mm (2 feet) deep. The standard UK rule is post length = panel height + 600mm burial, so a 1.83m (6ft) panel uses a 2.4m (8ft) post with 600mm in the ground. For exposed, windy or coastal sites, go to 750mm. (You will sometimes see a rough 'one-third underground' heuristic, but the panel height + 600mm method is the convention used by UK fencing suppliers and is what we recommend.)
Gravel boards are highly recommended for fence panel installations. They sit between the ground and the bottom of the fence panel, protecting the panel from ground moisture, rot and soil contact. Standard gravel boards are 150mm (6 inches) high and the same width as the panel (typically 1.83m). They are much cheaper to replace than a full fence panel.
Besides panel fencing, consider a retaining wall for sloped boundaries — see our Retaining Wall Calculator for block, sleeper or gabion quantities. For garden decking next to a fence, use our Decking Calculator. If you need gravel for the fence line base, try our Gravel Calculator.
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Last updated: February 2026
Verified against UK standards · estimates only, confirm with your supplier.