TradesHow this works
Enter the total run, the height, and the picket style. The tool builds the full shopping list, posts, rails, pickets, and bags of concrete, and lays the two common post spacings side by side so you can see what the choice costs. Eight foot spacing uses the fewest posts and matches 8 foot rail lumber. Six foot spacing costs more posts and concrete but holds a tall or privacy fence steady in wind.
The run count is for a straight line. Add a post at every corner and on each side of a gate, and dig your holes below the local frost line so the posts do not heave. Confirm your actual picket boards before you buy, since the width and gap swing the count more than anything else.
Common questions
How far apart should fence posts be?
Eight feet is the standard for a wood fence because it matches 8 foot rail lumber, so there is no cutting and you use the fewest posts. Drop to six feet for a privacy fence or any fence six feet or taller, where the solid face catches wind and the top rail needs the extra support.
How many posts do I need?
For a straight run, divide the length by the post spacing, round up, and add one to close the end. So a 100 foot fence at 8 foot spacing is 14 posts. Add one more post at every corner and one on each side of every gate.
How many rails per section?
Roughly one horizontal rail for every 24 inches of height. That is two rails for a 4 foot fence, three for a 6 foot fence, and four for an 8 foot fence. Privacy fences lean toward the higher count so the boards do not bow.
How much concrete per fence post?
A standard 4x4 post sits in about an 8 inch diameter hole dug a third of the fence height deep, which is around two 50 pound bags of fast-setting concrete for a 6 foot fence. Cold climates dig below the frost line and loose soil wants a wider hole, both of which add bags.
How many pickets do I need?
Take the run in inches and divide by the picket width plus the gap. A privacy fence butts the boards tight, so a 100 foot run of 5.5 inch boards is about 219 pickets. A spaced picket fence leaves a gap, so it uses fewer boards for the same run.
Sources: Post spacing: 8 ft standard for wood fences, 6 ft for privacy and fences 6 ft or taller (Family Handyman) · Rails: about one per 24 in of height (2 at 4 ft, 3 at 6 ft, 4 at 8 ft) · Concrete: ~2 bags of 50 lb fast-setting mix per 4x4 post in an 8 in hole dug 1/3 of height (Bob Vila, Inch Calculator, SlabCalc). Engine version 1.0.0. Risk tier 1.