How fence counts work
Divide the run by your post spacing and round up for sections; posts are sections plus one. Privacy fences run three horizontal rails per section, pickets two. Picket count comes from the run in inches divided by picket-plus-gap — a 5.5-inch picket with a half-inch gap lands one picket every 6 inches.
Worked example
A 120-ft privacy fence at 8-ft spacing: 15 sections, 16 posts, 45 rails, and about 252 pickets with waste — plus 32 fifty-pound bags of concrete at two per post. Corners and direction changes each start a fresh run, so measure and calculate each leg separately, then add.
Posts are where fences live or die
Set posts a third of their height into the ground — 2 ft minimum for a 6-ft fence — and below the local frost line, or winter will lift them. Slope the concrete top away from the wood so water sheds, and let posts set fully before hanging rails. Every leaning fence you've ever seen skipped one of those three.