Board-on-Board Fence Calculator

Created by Luis Hoyos
Reviewed by Dominika Śmiałek, MD, PhD candidate
Based on research by
The Wood Database Dimensional Shrinkage
Last updated: Mar 22, 2023

Welcome to this board-on-board fence calculator, a tool created to know:

  • How many pickets a board-on-board fence needs;
  • How many sections (aka panels) the board-on-board fence requires in total; and
  • Many more!

Keep reading this article to learn more about board-on-board privacy fences, the formulas, and how they differ from conventional fences.

Differences between conventional and board-on-board privacy fences

A fence typically consists of vertical boards or pickets attached to horizontal rails and located a distance apart, leaving gaps that allow air and light to pass through.

For total privacy, we can leave zero gaps between the pickets. Nevertheless, there's an issue: the wood can shrink, diminishing the width of the pickets and creating new openings. Fortunately, the board-on-board wood fence solves that.

In a board-on-board wood fence, we place each picket on top of another to compensate for future shrinkages.

Formulas for board-on-board fence calculation

For a board-on-board fence, we calculate the posts, rails, and sections (panels) as in a conventional fence (look at the formulas in our fence calculator).

The difference relies on how we calculate the number of pickets:

Number ofpickets=FencelengthPicketwidthPicketwidthPicketoverlap+1\scriptsize \begin{gather*}\rm Number\ of\\[-4px]\rm pickets \end{gather*} = \frac{\begin{gather*}\rm Fence\\[-5px]\rm length \end{gather*} - \begin{gather*}\rm Picket\\[-5px]\rm width \end{gather*}}{\begin{gather*}\rm Picket\\[-5px]\rm width \end{gather*} - \begin{gather*}\rm Picket\\[-5px]\rm overlap \end{gather*}} + 1

In the previous formula:

  • You must input the fence length, picket width, and picket overlap all in the same units.
  • If you obtain a decimal, round it up to the nearest integer (e.g., 4.6 ≈ 5 and 4.1 ≈ 5).

Picket overlap

🙋 tl;dr. Multiply the picket width by 0.24, and you'll get the recommended overlap.

  • We recommend using a picket overlap at least two times the expected width shrinkage.
  • In the worst case, that shrinkage will be 12% of the width.
  • Therefore, the rule of thumb is to use a picket overlap of 24% of the picket width.
  • Of course, that space must be enough to join the adjacent pickets.


How much overlap a board-on-board fence needs?

The recommended picket overlap for a board-on-board fence ranges from one to three inches, depending on the picket width and wood shrinkage:

  • For a 3½" picket width, a 0.8" overlap will be enough;
  • For a 5½" width, a 1.3" overlap is ok; or
  • For an 11½" width, you can use a 2.8" overlap.

How many pickets per 8-foot section my board-on-board fence needs?

To know how many pickets per 8-foot section your board-on-board fence needs, consider the width and overlapping:

  • If you use pickets of 5½" width with a 1½" overlapping, you need 24 pickets per section;
  • If you use pickets of 3½" width with a 1" overlapping, you need 38 pickets per section; and
  • For other widths or overlappings, use our board-on-board fence calculator.
Luis Hoyos
Number and length of posts needed
Fence length
Post space
Number of posts
Number of sections
Fence height
Post length
Number of rails needed
Rails per section
Number of rails
Number of pickets needed
Picket width
Picket overlapping
Number of pickets
Fence calculator: fence parts
To know how much concrete you need for the posts, visit the post hole concrete calculator.
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