Enter your fence run length and post spacing, set the rails per bay and picket size, and get the posts, rails, pickets and bags of post-mix concrete you need. Works in feet/inches or metres/millimetres.
Rails
24 · 180 ft
Pickets / boards
198
Bays
8
Post-mix bags
18
It works for any wood or timber fence - picket, close-board, board-on-board or pre-made panels. A fence run is divided into bays no wider than the post spacing. Each bay is one panel; posts close each bay, rails span them, and pickets or boards clad the run:
bays = ceil(run length ÷ post spacing)
posts = bays + 1
rails = bays × rails per bay
pickets = ceil(run length ÷ (picket width + gap) × wastage)
concrete = posts × bags per post
Bays round up so no gap is ever wider than your spacing - it is the post count people run short on, so the estimate stays on the generous side. Building an L-shaped, three-sided or full perimeter fence? Add a run for each straight length and the quantities pool, with a post counted at every corner - so a whole boundary is just as easy to total as a single run. All math runs in exact metric internally, so switching units never changes the answer.
This example follows the unit system you pick in the calculator above.
A 60 ft run at 8 ft post spacing, 3 rails per bay, 3.5 in pickets with a 0.5 in gap, 10% wastage, 2 bags of post-mix per post:
| Part | Rule of thumb |
|---|---|
| Post spacing | 1.8-3 m (6-10 ft); 2.4 m (8 ft) is the common default |
| Rails per bay | 2 up to 1.2 m, 3 for privacy height, 4 over 1.8 m |
| Post depth | About a third of the above-ground height, in concrete |
| Post-mix | 1-2 bags per standard post; more for tall or exposed posts |
| Picket gap | 0 for close-board/privacy, or the picket width for a classic spaced look |
Go deeper on any part of the job:
Divide the run length by the post spacing, round up to get the number of bays, then add one for the closing post. A 20 m run at 2.4 m spacing needs ceil(20 ÷ 2.4) = 9 bays, so 10 posts; a 60 ft run at 8 ft spacing needs 8 bays and 9 posts. Add a fence run for each straight length above and the calculator totals the posts, sharing nothing at corners so you have a post for every junction.
Timber fence posts are usually set 1.8-3 m (6-10 ft) apart on centre, with 2.4 m (8 ft) the common default that suits standard rail and panel lengths. Closer spacing makes a stiffer fence in exposed or windy spots; wider spacing uses fewer posts but needs stronger rails. Pick the spacing above to match your panels or rails.
Use 2 rails for a fence up to about 1.2 m (4 ft) and 3 rails for a taller close-board or privacy fence, with a fourth on anything over about 1.8 m (6 ft). The calculator multiplies the number of bays by the rails per bay, and also gives the total linear length of rail to buy.
For a pre-made panel fence, the number of panels equals the number of bays - divide the run length by the panel width and round up. A 20 m run with 1.8 m panels needs ceil(20 ÷ 1.8) = 12 panels and 13 posts. Set the post spacing to your panel width above and the calculator counts the bays (panels) and posts for each run.
A typical 100 mm (4 in) post in a 300 mm wide hole takes one to two bags of fast-setting post-mix per post; heavier or taller posts in exposed spots can take more. Set the bags per post above - the default of 2 is a safe allowance for a standard garden fence - and the calculator multiplies by the post count.
Add each straight length as its own run so corners each get a full post. For a gate, the calculator counts the line posts; a gate also needs two strong hanging/latch posts and its own hardware, so add those separately. Heavy gates often need deeper, wider footings than the line posts.
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