Fence calculator
Enter the run and get every count at once — including the post that catches people out, because a fence always needs one more post than it has sections.
The off-by-one, and the spacing decision
Ten sections need eleven posts. It sounds obvious written down and it is the single most common shortfall on a fence material list, because people multiply length by spacing and stop there.
Eight-foot spacing is the usual default because rails and boards come in eight and sixteen foot lengths, so nothing is wasted. Six-foot spacing costs more posts but produces a noticeably stiffer fence, which is worth it in high wind or on a slope. Whatever you choose, the posts define the whole job — everything else follows from where they land.
Picket counts assume a nominal width, with the default of 5.5 inches matching a standard six-inch board's actual size. Set a gap if you are building a spaced or shadowbox fence rather than a solid privacy run; even a half-inch gap changes the picket count meaningfully over a long fence.
The concrete estimate of one bag per post is a rough guide for typical four-by-four posts in normal soil. Bigger posts, sandy ground, or deeper frost lines all push it higher — check the hole volume if you want to be exact.
Questions
How far apart should fence posts be?
Eight feet is standard and matches common lumber lengths. Six feet gives a stiffer fence and is worth the extra posts in windy spots or on uneven ground.
How deep do posts go?
A common rule is a third of the post's above-ground height, or below the local frost line — whichever is deeper. That depth, not the count, is what determines concrete per post.
Why does picket width default to 5.5 inches?
Because a nominal six-inch board actually measures about 5.5 inches. Using the nominal size would undercount your pickets across a long run.