Fence Calculator — Posts, Rails & Pickets

Post spacing sets everything else. Eight feet on center is the standard for wood privacy fence because rails come in eight and sixteen foot lengths, which means no waste and no mid-span splices. Six feet on center produces a noticeably stiffer fence and is worth the extra posts in high-wind regions or on any run over about six feet tall. Vinyl and preassembled panel fences have fixed spacing set by the panel width, usually six or eight feet, and cannot be adjusted.

Count corners, ends and gates separately. Every corner needs a post, every gate needs two posts sized heavier than line posts, and any change in grade steep enough to step the fence needs a post at each step. A 200 foot run with two corners and one gate does not need 26 posts — it needs those line posts plus the corner and gate posts, and gate posts in particular should be 6×6 rather than 4×4 because they carry a swinging load all day.

The accepted rule is that a post hole should be one third of the above-ground post height deep, and three times the post width in diameter. A 6 foot fence therefore wants a 24 to 30 inch deep hole, or deeper if your local frost line is below that. A 4×4 post takes a 10 to 12 inch diameter hole, which consumes roughly one and a half to two 50 lb bags of fast-setting post mix per hole.

Set posts on 4 to 6 inches of gravel so water can drain away from the end grain, crown the concrete above grade so it sheds water, and let the mix cure before hanging rails. Fast-setting mix is poured dry into the hole and water is added on top, which is why it is the standard for fencing — no mixing, and posts are workable within an hour. For heavy gates, use standard concrete mixed properly and give it a full day.

Fencing is quoted by the linear foot in the United States. Chain link runs $12 to $25 installed, pressure-treated wood privacy fence runs $25 to $45, cedar privacy $35 to $60, vinyl $30 to $60, and ornamental aluminum $40 to $75. Material-only cost for a DIY wood privacy fence is typically 40 to 50 percent of the installed price, with post-hole digging being the labor most homeowners underestimate.

Before you buy anything, confirm the property line with a survey rather than a fence your neighbor built, check the local permit requirement — many US cities require one over six feet and most HOAs restrict style and height — and call 811 for utility locates. That call is free, legally required in every state, and considerably cheaper than hitting a gas line with an auger.