Fence post & panel calculator
Posts, panels and postcrete from a fence run. Set the length and panel width — the rest updates as you go.
The run
Total run to be fenced.
1.83m (6ft) is the standard UK panel width.
Roughly 3x the post width.
Deeper for taller or more exposed fencing.
Posts required
— an exact fit.
Illustrative only. Assumes a straight run with a post at each end and every panel joint. Fast-set proprietary postmix products may need fewer bags per hole — check the product.
Fence panels are simple to count — the posts are where people come up short. A run of ten panels doesn't need ten posts, it needs eleven: one at each end, plus one at every joint between panels. Miss that and you're back at the merchant for a single extra post halfway through digging holes.
Why panel width rarely divides evenly
Standard UK fence panels are 1.83m (6ft) wide, and real fence runs are almost never an exact multiple of that. This calculator rounds up to a whole number of panels and shows the actual run they cover — usually a little more than what you asked for. The difference gets absorbed at the last bay: a narrower infill panel, or the run shifted slightly to land on a better line.
Post holes and concrete
Hole size drives how much concrete each post needs — a wider or deeper hole takes noticeably more. 300mm diameter and 450mm deep is a reasonable default for a standard garden fence; taller panels, exposed sites, or heavier gates need a bigger hole and more concrete to hold firm. The figure here uses general-purpose concrete bag yield; fast-set proprietary postmix products are often formulated to need less per hole, so check the specific product if you're using one.
A worked example
An 18.3m run in standard 1.83m panels is exactly 10 panels and 11 posts — a clean fit with nothing left over. At 300mm × 450mm holes, that's 3 bags of postmix per post, 33 bags in total.
What this doesn't cover
Corners, gates and changes of direction all need extra posts this straight-run figure doesn't account for — add one post per corner or gate opening. Ground conditions, tree roots and existing obstructions can also force holes off their ideal spacing on site.
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