Posts are bays plus one. Almost every fence calculator divides the run by the spacing and hands you a number that leaves you one post short at the far end.
Enter the run and your maximum post spacing. We'll work out the bays, the posts, the rails and the pickets — with the gaps spread evenly rather than leaving a sliver at one end.
Works in metric and US imperial — you choose at the start and can switch at any time. Every figure this calculator uses is published with its source, and the result comes with a printable order sheet. No account, no email, and nothing you type leaves your browser.
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Almost every fence calculator divides the run by the spacing and hands you a number that leaves you one post short at the far end. A 30 m run at 2.4 m maximum spacing is 13 bays — so 14 posts. This page also spreads the bays evenly rather than running full-width bays until the last one, which is what leaves a sliver of a panel at the end where everybody sees it.
End, corner and gate posts take the pull of the whole run, so they want to be one size up and set around 25% deeper than the intermediate posts — and a gate post takes more again, because it carries a swinging load all day. Post depth is roughly a third of the height above ground as a rule of thumb, and more in sandy or waterlogged soil. The concrete is a separate calculation: run the concrete calculator for the post holes.
Ground is not level and fences are, so decide early whether the fence steps down in bays or follows the slope — it changes the picket lengths and the look completely. Leave the posts to cure before hanging anything: a day at minimum, longer in cold weather, because rails fixed to green concrete pull the posts out of plumb. And boundary fences have legal implications — height limits, which side the rails face, and whose land the posts sit in. Worth a conversation with the neighbour before the digger arrives.
One more than the number of bays. A 30 m run at 2.4 m spacing is 13 bays and 14 posts. Dividing the run by the spacing and stopping there is the classic way to end up one post short at the far end.
Roughly a third of the height above ground as a rule of thumb, and deeper in sandy or waterlogged soil. End, corner and gate posts want to go around 25% deeper again, and be one size up.
A day at minimum, and longer in cold weather. Rails fixed to green concrete pull the posts out of plumb, and that cannot be corrected afterwards.
Decide before you order. Stepping down in bays and following the slope produce completely different looks, and they need different picket lengths — so it is a decision that has to come before the materials.