Fence Calculator

A fence is a row of sections. Divide each run's length by the post spacing and round up for the sections; each run needs one more post than it has sections, and each gate adds a post. Rails are the sections times the rails per section, and pickets are the fence length in inches divided by one picket's actual width plus the gap.

Pickets use the actual width: a 1x6 is 5-1/2 inches wide and a 1x4 is 3-1/2, so 100 ft of tight 1x6 privacy fence takes 219 pickets, not 200. Posts 8 ft on center match 8 ft rails; many builders go to 6 ft for tall fences or windy sites.

QUIKRETE's guide is to dig the hole about 3 times the post's width and a third of the post's total length deep, plus 6 inches for gravel in the bottom so water drains away from the post. For a 6 ft fence that is 3 ft in the ground, so a 9 ft post; the calculator rounds up to a stock 10 ft post. Where the ground freezes, go below the frost line. Your ZIP adds a reminder.

For a single post, the concrete calculator has a post hole option with round posts too.

Lumber prices move too much to print one national number. Enter your prices for a post, a rail, a picket, and a bag of concrete, and the ticket totals the materials and works out the cost per foot of fence. The defaults are examples only. Labor, gate hardware, fasteners, and stain are extra, so a contractor's quote per foot will be higher than the materials alone.

A fence order is heavy and long. 100 ft of 6 ft privacy fence is about 5,800 lb of dry lumber, concrete, and gravel, more than a half-ton's 1,150 lb payload. Fresh pressure-treated lumber weighs much more: a wet 4x4 x 10 ft post is about 52 lb.

Ten-foot posts stick out about 3.5 ft from a 6.5 ft bed, and 16 ft rails would stick out more than 4 ft, which on a commercial vehicle means a red or orange flag at least 18 inches square, and many states require one on any vehicle. The calculator checks both, and the board foot calculator weighs any other lumber list.

• Set each post a third of its length deep, with 6 inches of gravel under it for drainage, and below the frost line where the ground freezes. (QUIKRETE)
• Dig holes about 3 times the post width: 10 to 12 inches for a 4x4. (QUIKRETE)
• Space posts to match your rails. Eight-foot rails want posts 8 ft on center, so measure center to center, not gap to gap.
• Call 811 a few days before you dig, so buried lines get marked.

• Counting pickets on the nominal width. A 1x6 covers 5-1/2 inches, so you need about 9 percent more than 2 per foot suggests.
• Forgetting the extra post at every gate and at the end of every run.
• Setting posts too shallow. A third of the post's length goes in the ground, deeper where it freezes.
• Filling the post hole to the top with concrete. Stop a few inches below grade and slope it so water runs off.
• Digging before calling 811 to mark buried lines.