The plan
Post centres decide everything else. The calculator rounds the bays up so the spacing is never wider than the figure you put in, which is why a 12 m run at 1,930 mm centres gives seven bays rather than six — and why the last bay is short.
It sizes the posts, the gravel boards, the fixing counts and the postcrete from the same numbers, and it treats the post holes as a thing to consider rather than a quantity, because the depth depends on your ground.
Doing it, in order
- Set the line out and check the boundary first — a fence above the permitted height, or beside a highway, is a different job from a garden fence. The planning permission rules are where the limits for your position are set.
- Dig the post holes at the centres, and deeper in clay or on an exposed site than the minimum.
- Set the end posts first, then run a line between them so every post in the middle sits to the same height and line.
- Concrete each post in and brace it while it sets — the bags per hole the calculator uses are in the take-off below.
- Fix the gravel boards along the bottom, then the panels between the posts, cutting the last one to the short bay.
- Hang the gate last, onto its own posts, so it closes against a fence that has already stopped moving.
Don’t forget
- The gate No engine sizes a gate, so there is no quantity for it here. A gate needs its own posts — heavier than the fence posts — and its own hinges, latch and bracing, sized by the gate you buy. Use its fitting instructions, not a figure from this page.
- Post hole digging and spoil removal The calculator returns this as "as needed": holes want to be about 600 mm deep and 200 mm across, and the spoil has to go somewhere.
- Boundary rules Fences and the height they are allowed to reach are permitted development only up to a point, and the limits differ by position. Check before you dig.
- Arris rails and feather-edge boards The take-off includes 21 rails, because that is what feather-edge boards fix to. If you are screwing ready-made panels to the posts instead, that line does not apply to your job.
Material take-off for this plan
Worked out by the site’s own Fence for this plan’s dimensions, not typed in by hand.
The working
| Working | Value |
|---|---|
| Fence run | 12.00 m Timber panel & post — Posts sit between the panels, so each panel spans the post centres less the post thickness. |
| Bays to fill | 7 Post centres at 1,930 mm; last bay is 420 mm |
| Posts | 8 7 bays + 1 — 100 mm posts |
| Clear span between posts | 1,830 mm 1,930 mm centres − 100 mm post |
| Panels required | 7 panels 7 bays × 1 panel per bay (panel size 1,830 mm wide) |
| Gravel boards | 7 One per bay, slotted or screwed in under the panel |
| Arris rails | 21 rails 3 per bay for feather-edge boards |
| Postcrete | 16 × 20 kg bags 2 bags per hole × 8 holes |
What to order
| Material | Quantity | Notes |
|---|---|---|
| Fence panels, 1,830 mm wide | 7 panels | 7 bays of 1 panel each — the last bay is 420 mm, so cut one panel down. |
| Fence posts, treated timber (100 mm) | 8 posts | At 1,930 mm centres: 7 bays plus one post at each end. |
| Gravel boards | 7 boards | One per bay, cut to the 1,830 mm clear span between posts. |
| Arris rails (3 per bay) | 21 rails | Carry feather-edge boards. Not needed if you are screwing ready-made panels to the posts. |
| Feather-edge / clout nails (galvanised) | 360 nails (about 2 boxes of 250) | Rule of thumb: about 30 nails per metre of fence — one or two per board at each rail. Galvanised, or the fixings streak the timber within a year. |
| Coach screws for rails to posts | 42 screws | Rule of thumb: two per rail per post, so 21 rails take about 42. Stainless or galvanised, with a washer — a black screw into wet-treated timber does not last. |
| Postcrete (20 kg bags) | 16 bags | ≈ 320 kg — 2 bags per post hole (8 holes). |
| Post hole digging / spoil removal | as neededestimate | Holes want to be 600 mm deep and about 200 mm across — deeper in clay or on an exposed site. |
Post centres decide everything else: bays are rounded up so the spacing is never wider than you asked for, and the last bay absorbs the difference. Measure the run at the posts, not at the ground — a fence line follows the posts, and a diagonal run is longer than the straight measurement between its ends.
A fence and gate, planned out FAQs
How many fence panels do I need for a 12 m run?
7 panels of 1,830 mm with 8 posts, from the fence calculator. The run at 1,930 mm centres gives 7 bays, and the last bay is only 420 mm, so one panel is cut down.
How many posts for a 12 m fence?
8 posts of 100 mm, which is one more than the number of bays — a post at each end of every run. The calculator adds that end post automatically.
How much postcrete do I need?
16 bags of 20 kg, at 2 bags per hole over 8 holes. Deeper holes or a wider auger take more, so the bags-per-post figure is an input rather than a fixed rule.
How many nails and screws does a panel fence need?
The calculator returns about 360 galvanised nails and 42 coach screws for this run. The nails are for feather-edge boards to the rails; the screws are what fixes rails to posts, two per rail per post.