Free NZ fence calculator. Posts, rails, and palings for timber fences with concrete and waste allowance.
This calculator counts the posts, rails, palings, fixings and footing concrete in a timber paling fence, from the fence length and height. It is a take-off tool: it counts what a fence of that size needs, it does not design it.
Posts are the fence length divided by your post spacing, rounded up, plus one — the closing post at the end of the last bay. Bays are one fewer than the posts, and rails are the bay count times the number of rails you choose, either two or three.
Palings are the fence length in millimetres divided by the paling width, at either 75mm or 100mm, then 10% added.
Heights offered are 1.2m, 1.5m, 1.8m and 2.1m, with post sizes of 100 by 100mm or 125 by 125mm.
The concrete in each hole comes from CostMate's own footing module, the single place in the codebase that decides how much concrete goes in a hole. Sharing it is why the deck, fence and carport estimates stopped disagreeing with each other.
First, it used to fill the whole cylinder as though no post were standing in it. A 100 by 100 post through a 600mm embedment displaces about 0.006 cubic metres — roughly one bag saved every two holes.
Second, it used a flat 600mm depth at every fence height. Embedment now slides from about a third toward a half of the fence height, so a 2.1m fence gets a deeper hole than a 1.2m one. Before that, a builder who priced the same fence through CostMate got a different bag count from this free page.
The page also snaps the required post length up to a stock length, so what it reports is a post you can actually buy rather than a theoretical dimension.
Nails per paling and fixings per rail end are your inputs, not CostMate's assertion. Nailing patterns vary by builder and by job, so you supply the pattern and the geometry does the counting — the same approach the decking calculator takes with screws.
Post embedment, fence height and any retaining function are design decisions. Check them against your plans and your council, and confirm stock lengths with your merchant, before you order or build.