How to use the fence calculator
- Measure the fence line. Walk the full run with a measuring wheel or long tape and add up every side you will fence, in feet.
- Choose height and post spacing. Wood fences usually have posts every 8 feet, which matches standard 8 ft rails. Use 6 ft spacing in windy areas or for heavy boards.
- Add gates. Each gate needs its own opening and an extra post, since both sides of a gate need a sturdy post.
- Pick a picket style. Privacy fences butt boards tight together. Shadowbox fences alternate boards on both sides of the rails. Traditional picket fences leave a gap.
Fence formulas
Posts = sections + 1 + one extra per gate
Rails = sections × 2 (fences up to 5 ft) or × 3 (6 ft and taller)
Pickets = fence length (in) ÷ (picket width + gap), plus 5%
Worked example
A 150 ft, 6 ft tall privacy fence with one 4 ft gate and posts every 8 ft has 146 ft of fencing. That is 19 sections, so you need 21 posts (19 + 1 + 1 for the gate) and 19 × 3 = 57 rails. With 5.5 inch pickets and no gap, 146 × 12 ÷ 5.5 = 319 pickets, or 335 with 5% extra. Setting 21 posts 3 ft deep in 10 inch holes takes about 49 bags of 80 lb concrete.
How deep should fence posts be?
A common rule is to bury one third to one half of the post's height above ground, and never less than 2 feet. A 6 ft fence needs posts about 9 ft long set roughly 3 ft deep. In cold climates, go below the frost line so the ground cannot heave the posts. Holes should be about three times the post width: 10 to 12 inches for a 4 × 4 post.
Tips before you build
- Call 811 before you dig. It is free in the US and marks buried utility lines.
- Check property lines and permits. Many towns limit fence height, require a permit, or set a distance from the line.
- Use ground-contact lumber for posts. Look for pressure-treated posts rated for ground contact, or use steel posts with wood brackets.
- Set corner and end posts first, run a string line between them, then set line posts to the string.
Pouring a footing or a slab for the gate area? Use the concrete calculator.
Frequently asked questions
How many fence posts do I need for 100 feet?
With posts every 8 feet, a straight 100 ft run has 13 sections and needs 14 posts. Add one more post for each gate.
How far apart should fence posts be?
Most wood fences place posts 6 to 8 feet apart, center to center. Eight feet matches standard rail lengths and is the most common choice.
How many pickets are in a foot of fence?
With standard 5.5 inch wide pickets and no gap, there are about 2.2 pickets per foot of privacy fence.
How much concrete do I need per fence post?
A 10 inch hole, 3 ft deep, around a 4 × 4 post needs about 1.4 cubic feet of concrete, which is roughly 2 to 3 bags of 80 lb mix or 3 to 4 bags of 50 lb fast-setting mix.
How many rails does a fence section need?
Two rails for fences up to about 5 ft tall, and three rails for 6 ft and taller privacy fences to stop the boards from warping.
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Last updated October 2026.