Fence Calculator

Sections are your total length divided by post spacing, rounded up. Post count is sections plus one for each separate straight run, a single straight fence needs one more post than it has sections, because both ends need one.

Standard spacing is 6 to 8 ft. Eight feet is common because lumber comes in 8 ft lengths, but 6 ft spacing makes a noticeably more rigid fence and is worth it for tall privacy panels that catch wind.

Set posts one third of their above-grade height into the ground, with a 2 ft minimum. A 6 ft privacy fence wants 2 ft in the ground, so buy 8 ft posts. In regions with deep frost, go below the frost line regardless of what the one-third rule says, or the fence will heave.

Hole diameter should be about three times the post width, a 4 × 4 post wants a 10 to 12 inch hole. Concrete volume per post is the hole volume minus the post itself.

Put a few inches of gravel in the bottom of each hole before the post. It lets water drain away from the end grain instead of pooling around it, which is where wood posts almost always start rotting.

Picket count depends on the board width plus the gap between boards, together, the pitch. A solid privacy fence has no gap, so pitch equals board width and a 5.5 inch board gives about 2.2 boards per foot.

A spaced picket fence with 3.5 inch boards and 2 inch gaps has a 5.5 inch pitch, so it needs less than half the boards of a solid fence over the same run.