A take-off for contractors, not a homeowner's guess. Run length, height and gates in; panels, posts, gravel boards and postmix out, with the cut panel, the post length, a materials cost and a labour estimate. It is a small version of the engine in case study 003 — 57 catalogue items and 29 rules — with your prices in it.
Fencing take-offs are arithmetic that people do wrong under pressure. Subtract the gates from the run, divide by the panel width, round up: that is your bays, and everything else follows from it — panels, boards, posts, postmix, post length, and the width of the awkward last panel. Put your own prices in and it becomes a materials cost with a labour estimate underneath.
Start with the length the fence actually covers: the total run minus the gate openings. Divide that by the panel width and round up — you cannot buy 15.85 panels — and that is the number of bays. The remainder is the cut panel at the end, which the tool shows you rather than hiding in the rounding, because an eleven-inch sliver at the end of a run is a thing worth knowing before the van is loaded.
From the bays everything else falls out. One panel and one gravel board per bay. Posts are bays plus one for a straight run, then one more for each gate — a gate needs two posts and shares one with the fence — and one more for each corner, because a change of direction ends one run and starts another. Postmix is your bags per post times posts. Post length is the height above ground plus the hole depth plus the gravel board, which is why a 1.8 m fence on 150 mm boards in 600 mm holes needs 2.55 m posts and not 2.4.
The geometry above is the easy half, and any competent surveyor can do it on the tailgate. What the surveyor cannot reliably hold is the prices — and in the fencing business this engine was built for, that was the whole problem. Rates came from memory or a printed list in the van, so whether a job was priced correctly depended on which surveyor took it and whether their list was current. A supplier increase only reached the customer when it reached every surveyor's memory.
The fix was not a cleverer take-off. It was holding one price book — 57 catalogue items and 29 rules seeded from the firm's own spreadsheet — so the same drawing produces the same price whoever drew it, and a rise entered once applies to every quote from that moment. The prices you type into this page are the tiny version of that book. If they live anywhere other than one central list in your business, that is the thing to fix before the arithmetic.
The defaults: a 30 m run, 1.8 m high, 1.83 m panels, one 1 m gate, one corner. Fence length after the gate is 29 m; 29 ÷ 1.83 is 15.85, so 16 bays with a 1.55 m cut panel at the end. Sixteen panels, sixteen gravel boards, 19 posts (16 + 1 + 1 gate + 1 corner), 38 bags of postmix at two a post, and 2.55 m posts. At £32 a panel, £14 a post, £9 a board, £6 a bag and £120 for the gate, with 5% waste, materials come to about £1,330. At three-quarters of an hour a bay and £25 an hour, labour is twelve hours and £300. About £1,630 before margin.
Use it on the tailgate, and notice how much of it depends on the prices you typed. If those prices are in a spreadsheet, a surveyor's memory or a printed list, the take-off is only as good as whichever of those was current on the day. The operations audit starts exactly here for a trades business: where the prices live, who is allowed to quote, and what happens to your growth when you cannot hire another one of them. The other calculators put numbers on the rest of it, and the short version of the method is on the byHoratio homepage.
Bays plus one for a straight run, plus one extra for each gate and one for each corner. Bays are the fence length after gate openings divided by the panel width, rounded up. So a 29 m run of 1.83 m panels is 16 bays and 17 posts; add a gate and a corner and it is 19. Order posts long enough for the height above ground, the depth in it and the gravel board — 2.55 m for a 1.8 m fence on 150 mm boards in 600 mm holes.
Two 20 kg bags per post is the usual allowance for a 600 mm hole with a 100 mm post; heavier posts, deeper holes or wider holes in soft ground take three. The calculator multiplies your bags per post by the post count, so change the figure to match how your crew actually sets posts rather than what the bag says.
The tool shows it rather than rounding it away. If the last bay is under about 300 mm it is usually worth shortening the run slightly or moving a gate so the final panel is a sensible width — you save a panel and a post and the fence looks right. Anything wider is simply cut on site, and the production engine in case study 003 draws the cut panel on the plan so the crew can see it before the van is loaded.
Not on its own, and that is the point of the page. The geometry is the easy half. What makes a quote reliable is where the prices come from: one central price book that every surveyor quotes from, so a supplier rise reaches every quote the moment it is entered. In the fencing business this was 57 items and 29 rules seeded from their own spreadsheet, and it meant a surveyor needed a tape measure rather than pricing knowledge. This calculator is the demonstration; that system is the product.
No — the bay logic is for panel-and-post. Closeboard is taken off by post centres, arris rails per bay and boards per metre with an overlap, which is a different set of rules. It is one of the fencing families the production engine handles and this page does not.
If the answer is one or two people who know the prices, that is the growth ceiling. Move the price book into a system and a surveyor needs a tape measure, not a memory. Twenty minutes, no deck, no pitch.
HORATIO@BYHORATIO.COM
The full engine: survey, drawing, pricing and three documents from one site visit, live in 11 days.
What inconsistent pricing costs a year when prices live in heads and spreadsheets.
The hire, the charge-out rate, the cost of standing still, and more.